Back to EveryPatent.com
| United States Patent |
6,065,339
|
|
Takeuchi
, et al.
|
May 23, 2000
|
Vibration gyro sensor, combined sensor and method for producing
vibration gyro sensor
Abstract
A vibration gyro sensor is constructed as follows. Namely, a detecting
piezoelectric/electrostrictive element 12, which detects displacement
generated in a direction perpendicular to a direction of vibration of a
vibrator 2 when the vibrator is rotated, is provided on a detecting
section. The detecting section is constructed by an integrated fired
product made of ceramics together with the vibrator 2 and a support base
4. The detecting section is constructed by a first plate-shaped section 6
which is more thin-walled than the vibrator 2 and which has its principal
surface extending in the direction of vibration. The
piezoelectric/electrostrictive element 12 is formed in an integrated
manner on the first plate-shaped section 6 in accordance with a film
formation method. Further, a thin-walled second plate-shaped section 8,
which is provided for decreasing rigidity in the direction of vibration
and facilitating the vibration for the vibrator 2, is formed in an
integrated manner so that its principal surface extends in the direction
perpendicular to the direction of vibration. Accordingly, it is possible
to obtain the vibration gyro sensor made of ceramics having excellent
sensitivity, in which the characteristics of the vibrator are scarcely
affected by an ambient magnetic field, processing or machining can be
easily performed, and the electric characteristics can be advantageously
adjusted.
| Inventors:
|
Takeuchi; Yukihisa (Nishikamo-gun, JP);
Namerikawa; Masahiko (Inazawa, JP);
Shibata; Kazuyoshi (Mizunami, JP);
Ohnishi; Takao (Nishikasugai-gun, JP)
|
| Assignee:
|
NGK Insulators, Ltd. (Nagoya, JP)
|
| Appl. No.:
|
952596 |
| Filed:
|
November 21, 1997 |
| PCT Filed:
|
March 28, 1997
|
| PCT NO:
|
PCT/JP97/01094
|
| 371 Date:
|
November 21, 1997
|
| 102(e) Date:
|
November 21, 1997
|
| PCT PUB.NO.:
|
WO97/37195 |
| PCT PUB. Date:
|
September 10, 1997 |
Foreign Application Priority Data
| Mar 29, 1996[JP] | 8-76434 |
| Aug 01, 1996[JP] | 8-203595 |
| Current U.S. Class: |
73/504.12 |
| Intern'l Class: |
G01C 019/00 |
| Field of Search: |
73/504.02,504.12,504.15,504.16
|
References Cited
U.S. Patent Documents
| 2247960 | Jul., 1941 | Michaels | 84/409.
|
| 2513340 | Jul., 1950 | Lyman | 264/1.
|
| 4628734 | Dec., 1986 | Watson | 73/505.
|
| 5533397 | Jul., 1996 | Sugitani et al. | 73/504.
|
| Foreign Patent Documents |
| 60-47913 | Mar., 1985 | JP.
| |
| 3-90079 | Sep., 1991 | JP.
| |
| 4-296657 | Oct., 1992 | JP.
| |
| 06347471 | Dec., 1994 | JP.
| |
| 7-23689 | May., 1995 | JP.
| |
| 8-128830 | May., 1996 | JP.
| |
| 8-160064 | Jun., 1996 | JP.
| |
| 8-178667 | Jul., 1996 | JP.
| |
| 8-201064 | Aug., 1996 | JP.
| |
| 8-304081 | Nov., 1996 | JP.
| |
| 9-89574 | Apr., 1997 | JP.
| |
Primary Examiner: Williams; Hezron
Assistant Examiner: Moller; Richard A.
Attorney, Agent or Firm: Wall Marjama Bilinski & Burr
Claims
What is claimed is:
1. A vibration gyro sensor comprising at least one vibrator subjected to
excited vibration effected by at least one driving means, a support base
for supporting said vibrator at a proximal end thereof, and at least one
detecting section including at least one detecting
piezoelectric/electrostrictive element for detecting displacement
generated in a direction perpendicular to a direction of vibration of said
vibrator when said vibrator is rotated, said vibration gyro sensor
including:
said detecting section composed of an integrated fired product made of
ceramics together with said vibrator and said support base, said detecting
section being constructed by a first plate-shaped section which is more
thin-walled than said vibrator and which has a principal surface extending
in said direction of vibration;
said detecting piezoelectric/electrostrictive element formed in an
integrated manner on said first plate-shaped section in accordance with a
film formation method; and
at least one thin-walled second plate-shaped section for decreasing
rigidity in said directions of vibration and facilitating said vibration,
said second plate-shaped section being provided for said vibrator in an
integrated manner so that a principal surface thereof extends in said
direction perpendicular to said direction of vibration.
2. The vibration gyro sensor according to claim 1, wherein:
said vibrator is provided with a thin-walled excisable section extending
from a forward end thereof; and
a resonance frequency of said vibrator is adjusted in accordance with an
amount of excision of said excisable section.
3. The vibration gyro sensor according to claim 1, wherein two of said
vibrators are supported in parallel to one another by said support base,
and said two vibrators are vibrated by said driving means in an excited
manner in mutually opposite directions.
4. The vibration gyro sensor according to claim 1, wherein said driving
means comprises:
a third plate-shaped section which is more thin-walled than said vibrator
and which is composed of said integrated fired product made of ceramics
together with said vibrator; and
a driving piezoelectric/electrostrictive element formed in an integrated
manner on said third plate-shaped section in accordance with said film
formation method.
5. The vibration gyro sensor according claim 3, wherein:
a support bar is arranged at a position which is located between said two
vibrators and which is separated from said vibrators; and
said support bar is supported in an integrated manner by said support base
together with said two vibrators.
6. The vibration gyro sensor according to claim 1, wherein said support
base is constructed by an attachment frame which is disposed outside said
vibrator and separated therefrom by a predetermined distance so that said
vibrator is surrounded thereby.
7. The vibration gyro sensor according to claim 3, wherein said driving
means is provided in an integrated manner between said two vibrators.
8. The vibration gyro sensor according to claim 3, wherein said driving
means is provided in an integrated manner between said second plate-shaped
sections.
9. The vibration gyro sensor according to claim 5, wherein said driving
means are provided in an integrated manner between said support bar and
said vibrators respectively.
10. The vibration gyro sensor according to claim 5, wherein said driving
means are provided in an integrated manner between said support bar and
said second plate-shaped sections respectively.
11. The vibration gyro sensor according to claim 6, wherein said driving
means are provided in an integrated manner between said attachment frame
and said vibrators respectively.
12. The vibration gyro sensor according to claim 6, wherein said driving
means are provided in an integrated manner between said attachment frame
and said second plate-shaped sections respectively.
13. A vibration gyro sensor comprising two vibrators arranged in parallel
to one another and mutually subjected to excited vibration, a frame for
surrounding said vibrators and supporting said vibrators at proximal ends
thereof, and detecting sections including detecting
piezoelectric/electrostrictive elements for detecting displacement
generated in a direction perpendicular to a direction of vibration of said
vibrators when said vibrators are rotated, said vibration gyro sensor
including:
said detecting sections composed of an integrated fired product made of
ceramics together with said vibrators and said frame, said detecting
sections being constructed by first plate-shaped sections which are more
thin-walled than said vibrators and which have principal surfaces
extending in said direction of vibration;
said detecting piezoelectric/electrostrictive elements formed in an
integrated manner on said first plate-shaped sections in accordance with a
film formation method;
a thin-walled second plate-shaped section for decreasing rigidity in said
direction of vibration and facilitating said vibration, said second
plate-shaped section being formed in an integrated manner for a portion
located between regions of said frame for supporting said two vibrators so
that a principal surface thereof extends in said direction perpendicular
to said direction of vibration;
a portion of said frame opposing to a region for forming said second
plate-shaped section, said portion being a third plate-shaped section
which is more thin-walled than said frame; and
a driving piezoelectric/electrostrictive element formed in an integrated
manner on said third plate-shaped section in accordance with said film
formation method, wherein:
said two vibrators are vibrated in an excited manner on the basis of
vibration of said frame effected by said driving
piezoelectric/electrostrictive element.
14. The vibration gyro sensor according to claim 13, wherein:
each of said vibrators is provided with a thin-walled excisable section
extending from a forward end thereof; and
a resonance frequency of said vibrator is adjusted in accordance with an
amount of excision of said excisable section.
15. The vibration gyro sensor according to claim 13, wherein an attachment
section for fixing said frame is formed in an integrated manner on an
outer surface of a region of said frame for forming said second
plate-shaped section.
16. The vibration gyro sensor according to claim 15, wherein said
attachment section includes, in an integrated manner, an attachment frame
which is positioned outside said frame and separated therefrom by a
predetermined distance so that said frame is surrounded thereby.
17. A vibration gyro sensor comprising two vibrators arranged in parallel
to one another and mutually subjected to excited vibration, a support base
for supporting said vibrators at proximal ends thereof, and detecting
sections including detecting piezoelectric/electrostrictive elements for
detecting displacement generated in a direction perpendicular to a
direction of vibration of said vibrators when said vibrators are rotated,
said vibration gyro sensor including:
said detecting sections composed of an integrated fired product made of
ceramics together with said vibrators and said support base, said
detecting sections being constructed by first plate-shaped sections which
are more thin-walled than said vibrators and which have principal surfaces
extending in said direction of vibration;
said detecting piezoelectric/electrostrictive elements formed in an
integrated manner on said first plate-shaped sections in accordance with a
film formation method;
a thin-walled second plate-shaped section for decreasing rigidity in said
direction of vibration and facilitating said vibration, said second
plate-shaped section being formed in an integrated manner for a portion
located between regions of said support base for supporting said two
vibrators so that a principal surface thereof extends in said direction
perpendicular to said direction of vibration;
an attachment section provided with an attachment frame connected in an
integrated manner to an outer surface of a region for forming said second
plate-shaped section and disposed outside said two vibrators and said
support base while being separated therefrom by predetermined distances so
that said two vibrators and said support base are surrounded thereby;
third plate-shaped sections more thin-walled than said support base and
formed in an integrated manner to bridge said attachment frame and
portions of said support base located on both sides of said second
plate-shaped section respectively; and
driving piezoelectric/electrostrictive elements formed in an integrated
manner on said third plate-shaped sections in accordance with said film
formation method, wherein:
said two vibrators are vibrated in an excited manner on the basis of
vibration of said support base effected by said driving
piezoelectric/electrostrictive elements.
18. The vibration gyro sensor according to claim 17, wherein:
each of said vibrators is provided with a thin-walled excisable section
extending from a forward end thereof; and
a resonance frequency of said vibrator is adjusted in accordance with an
amount of excision of said excisable section.
19. A vibration gyro sensor comprising:
a vibrator having a major axis extending in a certain direction;
a support base extending in a direction perpendicular to said certain
direction, for supporting said vibrator at an end thereof;
a frame for surrounding said vibrator and said support base, with a frame
surface being parallel to a plane including said certain direction and
said extending direction of said support base; and
a detecting section provided with a detecting
piezoelectric/electrostrictive element attached between said support base
and said frame, for detecting strain generated when said vibrator is
rotated around an axis perpendicular to said plane, wherein:
all of said vibrator, said support base, and said detecting section are
constructed by an integrated fired product made of ceramics;
said detecting section is constructed by a first plate-shaped section which
is more thin-walled than said vibrator in its direction of height; and
said vibrator is supported by said support base at said end which is
constructed by a second plate-shaped section which is thin-walled in said
certain direction.
20. The vibration gyro sensor according to claim 19, wherein said detecting
section is constructed by a ring member formed between said support base
and said frame, and said first plate-shaped section provided in a bridged
manner in said ring member in parallel to said extending direction of said
support base.
21. The vibration gyro sensor according to claim 19, wherein at least two
of said vibrators are supported by said support base in parallel to one
another, and a driving means for vibrating said respective vibrators in an
excited manner in mutually opposite directions is disposed.
22. The vibration gyro sensor according to claim 21, wherein said driving
means includes:
a third plate-shaped section which is more thin-walled in its direction of
height than said vibrator and which is constructed by said integrated
fired product made of ceramics together with said vibrator; and
a driving piezoelectric/electrostrictive element formed on said third
plate-shaped section.
23. The vibration gyro sensor according to claim 21, wherein said driving
means is provided in an integrated manner between said two vibrators.
24. The vibration gyro sensor according to claim 23, wherein said driving
means is arranged on a line for connecting respective centers of gravity
of said both vibrators.
25. The vibration gyro sensor according to claim 21, wherein said driving
means is provided in an integrated manner between said respective
vibrators and said support base.
26. The vibration gyro sensor according to claim 21, further comprising a
reference means for performing feedback control so that said driving means
makes constant vibration.
27. The vibration gyro sensor according to claim 26, wherein said reference
means comprises:
a fourth plate-shaped section which is more thin-walled in its direction of
height than said vibrator and which is constructed by said integrated
fired product made of ceramics together with said vibrator; and
a reference piezoelectric/electrostrictive element formed on said fourth
plate-shaped section.
28. The vibration gyro sensor according to claim 26, wherein said reference
means is provided in an integrated manner between said respective
vibrators.
29. The vibration gyro sensor according to claim 26 or 27, wherein said
reference means are provided in an integrated manner between said
respective vibrators and said support base.
30. The vibration gyro sensor according to claim 19, further comprising a
vibration-applying section provided in an integrated manner between said
vibrator and said support base.
31. The vibration gyro sensor according to claim 30, wherein said
vibration-applying section comprises:
a fifth plate-shaped section arranged between said vibrator and said
support base and extending in parallel to a longitudinal direction of said
support base;
a sixth plate-shaped sections for connecting said support base to said
fifth plate-shaped section; and
a seventh plate-shaped section for connecting said vibrator to said fifth
plate-shaped section.
32. The vibration gyro sensor according to claim 30, wherein said driving
means is provided in an integrated manner between said respective
vibration-applying sections.
33. The vibration gyro sensor according to claim 30, wherein said driving
means is provided in an integrated manner between said vibration-applying
section and said support base.
34. The vibration gyro sensor according to claim 19, further comprising:
thin-walled first projections for adjusting a resonance frequency for
driving, possessed by said vibrator at free ends thereof; and
thin-walled second projections for adjusting a resonance frequency for
detection, possessed by said support base at both ends thereof in its
longitudinal direction, wherein:
said first and second projections are constructed by said integrated fired
product made of ceramics together with said vibrator and said support
base.
35. The vibration gyro sensor according to claim 34, wherein said first and
second projections are thin-walled in a direction of height with respect
to said vibrator.
36. The vibration gyro sensor according to claim 34, wherein said first and
second projections are thin-walled in said extending direction of said
support base with respect to said vibrator.
37. The vibration gyro sensor according to claim 22, wherein:
said third plate-shaped section of said driving means is also used as an
adjustment objective for a resonance frequency for driving; and
said first plate-shaped section of said detecting section is also used as
an adjustment objective for a resonance frequency for detection.
38. A vibration gyro sensor comprising at least one vibrator subjected to
excited vibration effected by a driving means, a support base for
supporting said vibrator at a proximal end thereof, and at least one
detecting section including at least one detecting
piezoelectric/electrostrictive element for detecting displacement
generated in a direction perpendicular to a direction of vibration of said
vibrator when said vibrator is rotated, said vibration gyro sensor
including:
said vibrator composed of an integrated fired product made of ceramics
together with said support base, said vibrator being constructed by a
first plate-shaped section which is more thin-walled than said support
base and which has a principal surface extending in said direction of
vibration;
said detecting section constructed by said first plate-shaped section and
said detecting piezoelectric/electrostrictive element formed in an
integrated manner on said first plate-shaped section in accordance with a
film formation method; and
at least one thin-walled second plate-shaped section for decreasing
rigidity in said direction of vibration and facilitating said vibration,
said second plate-shaped section being provided for said vibrator in an
integrated manner so that a principal surface thereof extends in said
direction perpendicular to said direction of vibration.
39. The vibration gyro sensor according to claim 38, wherein two of said
vibrators are supported in parallel to one another by said support base,
said driving means is arranged between said respective second plate-shaped
sections, and said two vibrators are vibrated by said driving means in an
excited manner in mutually opposite directions.
40. The vibration gyro sensor according to claim 38, wherein said driving
means comprises:
a third plate-shaped section which is more thin-walled than said support
base and which is composed of said integrated fired product made of
ceramics together with said second plate-shaped sections; and
a driving piezoelectric/electrostrictive element formed in an integrated
manner on said third plate-shaped section in accordance with said film
formation method.
41. The vibration gyro sensor according to claim 38, wherein said detecting
piezoelectric/electrostrictive element is formed in an integrated manner
on an approximately entire surface of said first plate-shaped section.
42. The vibration gyro sensor according to claim 38, wherein:
said first plate-shaped section has, on its back surface, a plurality of
recesses; and
said detecting piezoelectric/electrostrictive elements are formed in an
array of islands at positions on a front surface of said first
plate-shaped section corresponding to said plurality of recesses.
43. The vibration gyro sensor according to claim 38, wherein a thick-walled
block section is provided in an integrated manner between said first
plate-shaped section and said second plate-shaped section.
44. The vibration gyro sensor according to claim 38, wherein said support
base is constructed by a frame which is positioned outside said vibrators
and separated by predetermined distances so that said vibrators are
surrounded thereby.
45. The vibration gyro sensor according to claim 38, wherein said driving
means is provided in an integrated manner between said respective second
plate-shaped sections.
46. The vibration gyro sensor according to claim 43, where in said driving
means is provided in an integrated manner between said respective block
sections.
47. The vibration gyro sensor according to claim 44, wherein said driving
means is provided in an integrated manner between said block section and
said frame.
48. The vibration gyro sensor according to claim 38, further comprising a
reference means for performing feedback control so that said vibration of
said driving means is constant.
49. The vibration gyro sensor according to claim 48, wherein said reference
means comprises:
a fourth plate-shaped section which is more thin-walled in its direction of
height than said support base and which is constructed by said integrated
fired product made of ceramics together with said vibrator; and
a reference piezoelectric/electrostrictive element formed on said fourth
plate-shaped section.
50. The vibration gyro sensor according to claim 48, wherein said reference
means is provided in an integrated manner between said respective second
plate-shaped sections.
51. The vibration gyro sensor according to claim 48, wherein said driving
means is provided in an integrated manner on one plate-shaped section of
said respective second plate-shaped sections, and said reference means is
provided on the other second plate-shaped section.
52. The vibration gyro sensor according to claim 51, wherein:
a mediating section having a free end is provided in an integrated manner
at an approximately central portion of a side surface of said support base
facing to said vibrating section;
said driving means is provided in an integrated manner between one of said
second plate-shaped sections and said mediating section; and
said reference means is provided in an integrated manner between the other
second plate-shaped section and said mediating section.
53. The vibration gyro sensor according to claim 51, wherein:
a plurality of mediating sections each having a free end are provided in an
integrated manner at positions of both ends in a widthwise direction of
said support base facing to said vibrating sections;
said driving means is provided in an integrated manner between one of said
second plate-shaped sections and one of said mediating sections; and
said reference means is provided in an integrated manner between the other
second plate-shaped section and the other mediating section.
54. The vibration gyro sensor according to claim 38, wherein:
an attachment section for fixing said support base is provided in an
integrated manner on a surface opposite to a surface of said support base
on which said second plate-shaped sections are formed;
a fifth plate-shaped section, which is thin-walled in a widthwise direction
of said support base, is provided in an integrated manner between said
support base and said attachment section; and
a tuning fork is constructed by at least said support base and said
vibrators.
55. The vibration gyro sensor according to claim 54, wherein said
attachment section is constructed by an attachment frame which is
positioned outside said tuning fork and separated by predetermined
distances therefrom so that said tuning fork is surrounded thereby.
56. The vibration gyro sensor according to claim 55, wherein:
a support section is provided in an integrated and bridged manner so that a
pair of inner wall surfaces of said attachment frame, which extend along
said extending direction of said vibrators, are bridged by said support
section facing to said vibrators disposed thereover; and
said fifth plate-shaped section is provided in an integrated manner between
said support section and said support base.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration gyro sensor. In particular,
the present invention relates to a vibration gyro sensor (scope) for
detecting the angular velocity of rotation by utilizing the Coriolis force
generated when a vibrator is rotated while making vibration, and a method
for producing the vibration gyro sensor. The present invention also
relates to a combined sensor including the vibration gyro sensor.
2. Background Art
The gyro sensor (scope), which is a sensor for detecting the angular
velocity of rotation, has been hitherto used, for example, for inertial
navigation systems of aircraft and shipping. Recently, the gyro sensor has
been used for vehicle-carried navigation systems and for attitude control
systems of automatically guided robot vehicles. Further, the gyro sensor
has been used, for example, for picture blurring-preventive systems of VTR
cameras. In such circumstances, a compact type gyro sensor is required,
which is appropriately used in various fields as described above.
Accordingly, the vibration gyro sensor attracts attention.
As well-known, the vibration gyro sensor (scope) of this type has a basic
structure comprising a driving piezoelectric element and a detecting
piezoelectric element which adhere to a vibrator formed of a constant
resilience metal represented by the elinvar alloy. In a rectangular
coordinate system of x, y, z axes, when the vibrator is rotated about the
z axis while giving bending vibration in the x axis direction to the
vibrator by using the driving piezoelectric element, the Coriolis force
acts in the y axis direction to the vibrator. Accordingly, the bending
vibration in the y axis direction caused in the vibrator by the Coriolis
force is detected as a voltage by the aid of the detecting piezoelectric
element. The angular velocity is determined on the basis of the detected
voltage.
However, in the case of the conventional vibration gyro sensor as described
above, the amount of displacement of the vibrator, which is based on the
vibration induced by the driving piezoelectric element, is small.
Therefore, the voltage (electromotive force), which is detected by the
detecting piezoelectric element, is small. As a result, the conventional
vibration gyro sensor suffers from low sensitivity.
In addition, the driving piezoelectric element and the detecting
piezoelectric element are glued and fixed to the vibrator by using an
adhesive. Therefore, the adhesive intervenes between the vibrator and the
piezoelectric elements. As a result, the stress is absorbed by the
adhesive. This is problematic since the detection sensitivity is lowered.
When the vibrator comprises a member which is composed of a sound chip or a
tuning fork formed of an elinvar alloy, a problem arises in that the
characteristics of the vibrator tend to be affected by an ambient magnetic
field, because the elinvar alloy is a ferromagnetic material. Further, due
to the shape or the material of the vibrator as described above, there is
an implicit problem that it is difficult to perform processing or
machining when the resonant frequency of the vibrator is adjusted.
SUMMARY OF THE INVENTION
The present invention has been made is to solve all of the problems as
described above and provide a vibration gyro sensor having excellent
sensitivity. Another object of the present invention is to provide a
vibration gyro sensor made of ceramics, in which the characteristics of
the vibrator are barely affected by an ambient magnetic field, processing
or machining can be easily performed, and the electric characteristics can
be advantageously adjusted.
The present invention provides a vibration gyro sensor which is constructed
as a whole by an integrated fired product made of ceramics without using
any magnetic material. Therefore, the vibration gyro sensor according to
the present invention scarcely affected by any ambient magnetic field.
Further, the vibration gyro sensor includes first plate-shaped sections
and second plate-shaped sections which are thin-walled respectively and
which are provided as easily bendable sections in driving and detecting
directions for making displacement of vibrators respectively. Therefore,
large displacement is obtained in any of the detecting and driving
directions, thus giving a large electromotive force (voltage) generated
depending on the displacement detected by piezoelectric/electrostrictive
elements, and making it possible to effectively increase the detection
sensitivity. Especially, the detecting section has a structure to which
the stress is concentrated. Therefore, a large output is obtained.
Moreover, the vibration gyro sensor according to the present invention
includes the detecting piezoelectric/electrostrictive elements which are
formed in an integrated manner in accordance with a film formation method
on the first plate-shaped sections for giving the detecting sections
constructed by the integrated fired product made of ceramics. The
piezoelectric/electrostrictive elements directly contact with the first
plate-shaped sections without any intervening adhesive layer. Therefore,
any absorption of stress, which would be otherwise caused due to the
presence of such an adhesive layer, is effectively avoided. Accordingly,
the displacement (bending vibration) of the vibrators, which is caused by
the Coriolis force induced when the vibrators are rotated, can be
effectively detected by the piezoelectric/electrostrictive elements,
making it possible to advantageously contribute to the improvement in
sensitivity.
In the vibration gyro sensor according to the present invention, for
example, the electrode area of the piezoelectric/electrostrictive element
provided on the detecting section can be easily changed by using an
appropriate removing means such as a laser. Therefore, the vibration gyro
sensor also has such a feature that its electric characteristics are
easily adjusted.
In a preferred embodiment of the present invention, the vibrator is
provided with a thin-walled excisable section extending from a forward end
of the vibrator, and a resonance frequency of the vibrator is adjusted in
accordance with an amount of excision of the excisable section. The
thin-walled excisable section, which is provided at the end of the
vibrator, is an easily processible or machinable portion. The resonance
frequency of the vibrator can be easily adjusted to have a desired value
by providing such an excisable section for trimming beforehand, and
excising the excisable section by means of an appropriate excising means
such as laser machining and ultrasonic machining.
In another preferred embodiment of the present invention constructed as
described above, two of the vibrators are supported in parallel to one
another by the support base, and the two vibrators are vibrated by the
driving means in an excited manner in mutually opposite directions. In
this embodiment, the vibration gyro sensor may be constructed such that
the driving means comprises a third plate-shaped section which is more
thin-walled than the vibrator and which is composed of the integrated
fired product of ceramics together with the vibrator, and a driving
piezoelectric/electrostrictive element formed in an integrated manner on
the third plate-shaped section in accordance with the film formation
method.
In still another preferred embodiment of the present invention constructed
as described above, a support bar is arranged at a position which is
located between the two vibrators and which is separated from the
vibrators. The support bar is supported in an integrated manner by the
support base together with the two vibrators.
In still another preferred embodiment of the present invention constructed
as described above, the support base is constructed by an attachment frame
which is disposed outside the vibrator and separated therefrom by a
predetermined distance so that the vibrator is surrounded thereby.
Provision of the attachment frame makes it possible to tightly fix the
vibration gyro sensor, exhibiting a feature that a place for installing
the vibration gyro sensor can be selected with a large degree of freedom.
The following embodiments may be adopted for the position of arrangement of
the driving means. Namely, the driving means may be provided in an
integrated manner between the two vibrators. Alternatively, the driving
means may be provided in an integrated manner between the second
plate-shaped sections.
When the vibration gyro sensor includes the support bar, the driving means
may be provided in an integrated manner between the support bar and the
vibrators respectively, or the driving means may be provided in an
integrated manner between the support bar and the second plate-shaped
sections respectively.
When the vibration gyro sensor includes the attachment frame, the driving
means may be provided in an integrated manner between the attachment frame
and the vibrators respectively, or the driving means may be provided in an
integrated manner between the attachment frame and the second plate-shaped
sections respectively.
According to another aspect, there is provided a second type of the
vibration gyro sensor according to the present invention, wherein a second
plate-shaped section and a third plate-shaped section are provided in an
integrated manner at opposing regions on a frame for supporting two
vibrators, and a driving piezoelectric/electrostrictive element is formed
in an integrated manner on the third plate-shaped section so that the two
vibrators may be vibrated in an excited manner in accordance with
deformation vibration of the frame effected by the driving
piezoelectric/electrostrictive element.
The vibration gyro sensor, which makes the deformation vibration of the
frame as described above, advantageously adopts a structure in which an
attachment section for fixing the frame is formed in an integrated manner
on an outer surface of a region of the frame for forming the second
plate-shaped section, in order to facilitate fixation of the frame.
Alternatively, a structure is advantageously adopted, in which the
attachment section includes, in an integrated manner, an attachment frame
which is positioned outside the frame and separated therefrom by a
predetermined distance so that the frame is surrounded thereby. Such an
attachment frame realizes tight fixation of the vibration gyro sensor.
According to still another aspect, there is provided a third type of the
vibration gyro sensor according to the present invention, which is
different from the vibration gyro sensors of the foregoing two types.
Namely, support base portions for supporting two vibrators respectively
are individually subjected to deformation vibration respectively by the
aid of driving piezoelectric/electrostrictive elements provided on third
plate-shaped sections for making connection to an attachment frame
disposed outside. Accordingly, the two vibrators, which are supported by
the respective support base portions, are individually vibrated in an
identical plane, respectively.
The vibration gyro sensor of the third type is also advantageously
constructed such that each of the vibrators has a thin-walled excisable
section extending from a forward end thereof, in the same manner as the
vibration gyro sensor of the second type. The resonance frequency of the
vibrator is adjusted in accordance with the amount of excision of the
excisable section. Accordingly, trimming can be easily performed by means
of an excising means such as laser machining and ultrasonic machining.
Thus it is possible to easily adjust the resonance frequency.
According to still another aspect, there is provided a fourth type of the
vibration gyro sensor according to the present invention. At first, when
an angular velocity is applied around an axis perpendicular to a plane
which includes a certain direction and an extending direction of the
support base in a state of vibration of the vibrators, the force (Coriolis
force) directed in the certain direction is generated in an alternating
manner in the vibrators in accordance with the vibration. As a result, a
force acts on the detecting sections in the certain direction, and the
detecting sections are vibrated by the force. Namely, rotational vibration
is generated around the axis of rotation at portions comprising the
vibrators and the support base. The generated vibration is detected as an
electromotive force (voltage) by the piezoelectric/electrostrictive
elements of the detecting sections.
According to the present invention, all of the vibrators, the support base,
and the detecting sections are constructed by an integrated fired product
made of ceramics. Therefore, there is no magnetic material such as the
conventional elinvar alloy in the materials for constructing the vibration
gyro sensor. As a result, the characteristics of the sensor are not
affected by any ambient magnetic field.
The detecting section is constructed by the first plate-shaped section
which is more thin-walled than the vibrator in its direction of height,
and thus it has the structure having low rigidity. Therefore, large strain
or distortion is obtained in the detecting section when the vibration is
generated around the axis of rotation by the angular velocity, and thus
the detection sensitivity of the piezoelectric/electrostrictive element is
greatly improved.
Especially, the vibration gyro sensor according to the present invention
functions such that the vibration is generated in the detecting section
only when the angular velocity is applied. Therefore, the output (null
voltage), which is obtained from the piezoelectric/electrostrictive
element in a state in which no angular velocity is applied, is extremely
small. Thus the detection sensitivity is greatly improved. Moreover, the
probability of fatigue fracture at the detecting section due to vibration
is lowered, and it is possible to contemplate a long service life of the
sensor.
The vibration gyro sensor according to the present invention has the
structure not for measuring the angular velocity around the major axis of
the vibrator, but for measuring the angular velocity around the axis
perpendicular to the plane which includes the certain direction and the
extending direction of the support base. Therefore, the vibrators, the
support base, and the frame can be made thin in their direction of height.
Thus it is possible to facilitate realization of a compact size and a
light weight of the sensor.
The vibrator has the structure including no thin-walled detecting section
and supported singly by the support base which has high strength.
Therefore, the vibrator itself is allowed to have a large mass.
Accordingly, the Coriolis force (Fc=2 mv.OMEGA.) generated in the vibrator
is increased, and hence it is possible to realize a high sensitivity in
relation to the detection of strain effected by the detecting section.
It is preferable in the vibration gyro sensor according to the present
invention that each of the detecting sections is constructed by a ring
member formed between the support base and the frame, and the first
plate-shaped section provided in a bridged manner in the ring member in
parallel to the extending direction of the support base.
In this embodiment, when the angular velocity is applied around the axis
perpendicular to the plane which includes the certain direction and the
extending direction of the support base is in a state in which the
vibrator is rotated, the force acts in the certain direction on the
detecting section. The action of the force allows the ring member to make
vibration while giving an elliptic configuration having its major or minor
axis directed in the certain direction. The vibration of the ring member
along the certain direction is detected as an electromotive force
(voltage) by the piezoelectric/electrostrictive element.
It is preferable for the vibration gyro sensor according to the present
invention that at least two of the vibrators are supported by the support
base in parallel to one another, and a driving means for vibrating the
respective vibrators in an excited manner in mutually opposite directions
is disposed between the two vibrators. In this embodiment, the at least
two vibrators make vibrations in the mutually opposite directions, namely
in directions to make mutual separation and approach in one plane (in the
plane which includes the certain direction and the extending direction of
the support base). It is preferable that the driving means includes, for
example, a third plate-shaped section which is more thin-walled in its
direction of height than the vibrator and which is constructed by the
integrated fired product of ceramics together with the vibrator, and a
driving piezoelectric/electrostrictive element formed on the third
plate-shaped section.
It is preferable for the vibration gyro sensor constructed as described
above that the driving means is provided in an integrated manner between
the two vibrators. The-driving means is preferably arranged on a line for
connecting respective centers of gravity of the both vibrators. This
arrangement is advantageous to improve the sensitivity of the detecting
section, since the at least two vibrators can make mutual approach and
separation efficiently. Alternatively, the driving means may be provided
in an integrated manner between the respective vibrators and the support
base.
It is preferable that the vibration gyro sensor constructed as described
above further comprises a reference means for performing feedback control
so that the vibration of the driving means is constant. The reference
means may comprise a fourth plate-shaped section which is more thin-walled
in its direction of height than the vibrator and which is constructed by
the integrated fired product made of ceramics together with the vibrator,
and a reference piezoelectric/electrostrictive element formed on the
fourth plate-shaped section.
The reference means may be provided in an integrated manner between the
respective vibrators. Alternatively, the reference means may be provided
in an integrated manner between the respective vibrators and the support
base.
It is preferable that the vibration gyro sensor constructed as described
above further comprises vibration-applying sections provided in an
integrated manner between the respective vibrators and the support base.
The vibration-applying section may comprise a fifth plate-shaped section
arranged between the vibrator and the support base and extending in
parallel to a longitudinal direction of the support base, a sixth
plate-shaped sections for connecting the support base to the fifth
plate-shaped section, and a seventh plate-shaped section for connecting
the vibrator to the fifth plate-shaped section. In this embodiment, the
driving means may be provided in an integrated manner between the
respective vibration-applying sections. Alternatively, the driving means
may be provided in an integrated manner between each of the
vibration-applying sections and the support base.
It is preferable that the vibration gyro sensor constructed as described
above further comprises thin-walled first projections for adjusting a
resonance frequency for driving, provided at free ends of the vibrators,
and thin-walled second projections for adjusting a resonance frequency for
detection, provided at both ends of the support base in its longitudinal
direction, wherein the first and second projections are constructed by the
integrated fired product made of ceramics together with the vibrators and
the support base.
In this embodiment, the resonance frequency for driving can be adjusted by
applying a trimming treatment (excising treatment) to the first
projection, and the resonance frequency for detection can be adjusted by
applying a trimming treatment (excising treatment) to the second
projection. Namely, the resonance frequencies for driving and detection
can be independently adjusted respectively. Therefore, for example, it is
possible to avoid the inconvenience that the resonance frequency for
detection is affected by adjustment for the resonance frequency for
driving. When the resonance frequency is adjusted, it is preferable that
the resonance frequency for driving is firstly adjusted, and then the
resonance frequency for detection is adjusted.
For example, the first and second projections may be constructed to be
plate-shaped and thin-walled in a direction of height with respect to the
vibrators. Alternatively, the first and second projections may be
constructed to be plate-shaped and thin-walled in the extending direction
of the support base with respect to the vibrators. The former construction
is advantageous in that the trimming treatment can be easily performed by
means of, for example, laser beam scanning over the upper surface. In the
case of the latter construction, regions to be subjected to the trimming
treatment are disposed over entire surfaces perpendicular to the direction
of vibration of the vibrators, and hence an extremely excellent mass
balance is obtained. In this case, the trimming treatment is performed,
for example, by applying percussion such as ultrasonic waves after laser
radiation so that unnecessary portions are excised.
It is preferable for the vibration gyro sensor constructed as described
above that the third plate-shaped section of the driving means is also
used as an adjustment objective for a resonance frequency for driving, and
the first plate-shaped section of the detecting section is also used as an
adjustment objective for a resonance frequency for detection.
Specifically, the resonance frequency for driving is adjusted by
trimming-treating, in the widthwise direction, the third plate-shaped
section of the driving means, and the resonance frequency for detection is
adjusted by trimming-treating, in the widthwise direction, the first
plate-shaped section of the detecting section. Namely, this embodiment
lies in the method in which the resonance frequencies for driving and
detection are adjusted by changing spring constants of the first and third
plate-shaped sections, rather than that the resonance frequencies for
driving and detection are adjusted by changing masses of the vibrator and
the support base.
In this embodiment, it is unnecessary to form the first and second
projections at the free ends of the vibrators and at the both ends of the
support base in the longitudinal direction respectively. Accordingly, the
production steps can be simplified. Further, since the regions to be
subjected to the trimming treatment are thin-walled, the resonance
frequency can be easily adjusted. Unlike the method in which the resonance
frequency is adjusted by changing the mass, the resonance frequency for
driving and the resonance frequency for detection can be adjusted
completely independently.
According to still another aspect, there is provided a fifth type of the
vibration gyro sensor according to the present invention, wherein
vibrators are constructed by wide and lengthy first plate-shaped sections
respectively. Accordingly, the mass and the moment of the vibrator are
increased. As a result, the velocity (.varies. amplitude) brought about by
the driving vibration is increased. Therefore, it is possible to further
improve the sensitivity.
It is preferable that the detecting piezoelectric/electrostrictive element
is formed in an integrated manner on an approximately entire surface of
the first plate-shaped section. This embodiment is advantageous in the
case of the current-detecting system, because it is possible to accumulate
a large amount of electric charge.
It is preferable for the vibration gyro sensor constructed as described
above that the first plate-shaped section has, on its back surface, a
plurality of recesses, and the detecting piezoelectric/electrostrictive
elements as defined above are formed in an array of islands at positions
on a front surface of the first plate-shaped section corresponding to the
plurality of recesses. In this embodiment, the strength is decreased at
the portions of the first plate-shaped section at which the recesses are
formed. Therefore, when the first plate-shaped section is deformed by the
Coriolis force, large strain is generated at the portions at which the
recesses are formed as compared with other portions at which no recess is
formed. Accordingly, when the detecting piezoelectric/electrostrictive
elements are formed on the portions corresponding to the recesses, a large
detection output can be obtained, and the sensitivity can be further
improved.
It is preferable for the vibration gyro sensor constructed as described
above that a thick-walled block section is provided in an integrated
manner between the first plate-shaped section and the second plate-shaped
section. In this embodiment, owing to the presence of the block section,
it is possible to increase the strength of the boundary portion, which is
advantageous from a viewpoint of improvement in reliability.
The support base may be constructed by a frame which is positioned outside
the vibrators and separated by predetermined distances so that the
vibrators are surrounded thereby. When the support base has the form of
frame, it is possible to obtain a large degree of freedom for attachment,
and the rigidity is excellent. Therefore, this embodiment is preferred
from a practical viewpoint.
The driving means may be provided in an integrated manner between the
respective second plate-shaped sections. Alternatively, the driving means
may be provided in an integrated manner between the respective block
sections. Further alternatively, the driving means may be provided in an
integrated manner between the block section and the frame.
It is preferable that the vibration gyro sensor constructed as described
above further comprises a reference means for performing feedback control
so that the vibration of the driving means is constant. The reference
means may be provided in an integrated manner between the respective
second plate-shaped sections.
In still another embodiment, the driving means may be provided in an
integrated manner on one plate-shaped section of the respective second
plate-shaped sections, and the reference means may be provided on the
other plate-shaped section.
In this embodiment, it is possible to adopt a structure in which a
mediating section having a free end is provided in an integrated manner at
an approximately central portion of a side surface of the support base
facing to the vibrating section, the driving means is provided in an
integrated manner between one of the second plate-shaped sections and the
mediating section, and the reference means is provided in an integrated
manner between the other second plate-shaped section and the mediating
section.
It is also possible to adopt a structure in which a plurality of mediating
sections each having a free end are provided in an integrated manner at
positions of both ends in a widthwise direction of the support base facing
to the vibrating sections, the driving means is provided in an integrated
manner between one of the second plate-shaped sections and one of the
mediating sections, and the reference means is provided in an integrated
manner between the other second plate-shaped section and the other
mediating section.
It is preferable for the vibration gyro sensor constructed as described
above that an attachment section for fixing the support base is provided
in an integrated manner on a surface opposite to a surface of the support
base on which the second plate-shaped sections are formed, a fifth
plate-shaped section, which is thin-walled in a widthwise direction of the
support base, is provided in an integrated manner between the support base
and the attachment section, and a tuning fork is constructed by at en
least the support base and the vibrators. In this embodiment, the fifth
plate-shaped section functions as a support rod for supporting the tuning
fork. Therefore, it is easy to discriminate necessary modes for the
vibration gyro sensor from unnecessary modes, and it is possible to
improve the detection accuracy.
It is preferable for the vibration gyro sensor constructed as described
above that the attachment section is constructed by an attachment frame
which is positioned outside the tuning fork and separated by predetermined
distances therefrom so that the tuning fork is surrounded thereby. In this
embodiment, it is possible to improve the detection accuracy. Further,
this embodiment is preferred, for example, from viewpoints of the degree
of freedom for attachment and rigidity, because the attachment section is
provided as the attachment frame.
In the embodiment provided with the attachment frame as described above, it
is possible to adopt a structure in which, a support section is provided
in an integrated and bridged manner so that a pair of inner wall surfaces
of the attachment frame, which extend along the extending direction of the
vibrators, are bridged by the support section facing to the vibrators
disposed thereover, and the fifth plate-shaped section is provided in an
integrated manner between the support section and the support base.
In this embodiment, even when the length of the fifth plate-shaped section
is elongated, the entire length of the sensor is not changed until within
a certain range. Therefore, it is possible to elongate the fifth
plate-shaped section, and it is possible to realize further improvement in
detection accuracy.
In still another aspect, the present invention makes it possible to
advantageously construct and realize a combined sensor by using those
provided with the attachment frame, of the vibration gyro sensors
described above, wherein a second attachment frame integrated with the
attachment frame is provided adjacent to the attachment frame, and another
sensor having a function different from that of the vibration gyro sensor
is supported in an integrated manner in the second attachment frame.
Especially, the conventional vibration gyro sensor merely realizes an
element having only one function. However, when an additional sensor
having another function is provided by utilizing the attachment frame as
described above, it is possible to easily provide a combined sensor or an
integrated sensor which not only functions as the vibration gyro sensor,
but also simultaneously realizes another function.
In still another aspect, the present invention lies in a method for
producing a vibration gyro sensor, comprising the steps of stacking and
integrating at least a substrate layer and a thin plate layer composed of
green sheets, followed by firing to produce a fired product including, in
an integrated manner, at least one or more vibrators each having a major
axis extending in a certain direction, a support base extending in a
direction perpendicular to the certain direction, for supporting the
vibrator at one end, a frame having its frame surface parallel to a plane
which includes the certain direction and the extending direction of the
support base, for surrounding the vibrator and the support base, and at
least one or more detecting sections attached between the support base and
the frame; forming at least one or more piezoelectric/electrostrictive
elements on at least the detecting sections in accordance with a film
formation method; adjusting a resonance frequency for driving by applying
a trimming treatment to a part of the vibrator; and adjusting a resonance
frequency for detection by applying a trimming treatment to a part of the
support base.
According to this method, it is possible to easily and highly reliably
produce the vibration gyro sensor having the structure in which the
support base and the vibrators are surrounded by the frame, and the
support base is connected to the frame via the detecting sections. The
resonance frequencies for driving and detection can be easily adjusted by
trimming-treating a part of the vibrators and a part of the support base
respectively. Therefore, this method is advantageous reducing the number
of production steps.
It is preferable to use, as the vibration gyro sensor, a vibration gyro
sensor comprising at least two of the vibrators supported in parallel to
one another by the support base, and a driving means provided between the
two vibrators for vibrating the respective vibrators in an excited manner
in mutually opposite directions, wherein the driving means includes a
third plate-shaped section which is more thin-walled in its direction of
height than the vibrators and which is composed of the integrated fired
product made of ceramics together with the vibrators, and a driving
piezoelectric/electrostrictive element formed on the third plate-shaped
section.
It is preferable that the adjustment for the resonance frequency for
driving is performed by applying a trimming treatment to a thin-walled
first projection protruding in an integrated manner from a free end of the
vibrator, and the adjustment for the resonance frequency for detection is
performed by applying a trimming treatment to thin-walled second
projections protruding in an integrated manner from both ends of the
support base in its longitudinal direction. In this embodiment, the
resonance frequency for driving can be adjusted by applying the trimming
treatment (excising treatment) to the first projection, and the resonance
frequency for detection can be adjusted by applying the trimming treatment
(excising treatment) to the second projection. Namely, the resonance
frequencies for driving and detection can be independently adjusted
respectively. Therefore, it is possible to avoid the inconvenience that
the resonance frequency for detection is affected by adjustment for the
resonance frequency for driving.
It is preferable that the adjustment of the resonance frequency for driving
is performed by applying a trimming treatment to the third plate-shaped
section in its widthwise direction, and the adjustment for the resonance
frequency for detection is performed by applying a trimming treatment to
the first plate-shaped section of the detecting section in its widthwise
direction.
This embodiment lies in the method in which the resonance frequencies for
driving and detection are adjusted by changing spring constants of the
first and third plate-shaped sections, rather than that the resonance
frequencies for driving and detection are adjusted by changing masses of
the vibrators and the support base. Therefore, it is unnecessary to form
the first and second projections at the free ends of the vibrators and at
the both ends of the support base in the longitudinal direction
respectively. Accordingly, the production steps can be simplified.
Further, since the regions to be subjected to the trimming treatment are
thin-walled, the resonance frequency can be easily adjusted. Unlike the
method in which the resonance frequency is adjusted by changing the mass,
the resonance frequency for driving and the resonance frequency for
detection can be adjusted completely independently.
It is preferable that the resonance frequency for detection is adjusted
after the resonance frequency for driving is adjusted.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically shows a perspective view illustrating a first
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 2 schematically shows an exploded perspective view illustrating the
vibration gyro sensor shown in FIG. 1.
FIG. 3 schematically shows a partial perspective view illustrating, in a
magnified manner, a portion of a first plate-shaped section of the
vibration gyro sensor shown in FIG. 1.
FIG. 4 schematically shows a perspective view illustrating a second
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 5 schematically shows a perspective view illustrating a third
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 6 schematically shows a perspective view illustrating a fourth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 7 schematically shows a perspective view illustrating a fifth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 8 schematically shows a perspective view illustrating a sixth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 9 schematically shows a perspective view illustrating a seventh
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 10 schematically shows a perspective view illustrating an eighth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 11 schematically shows a perspective view illustrating a ninth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 12 schematically shows a perspective view illustrating a tenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 13 schematically shows a perspective view illustrating an eleventh
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 14 schematically shows a perspective view illustrating a twelfth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 15 schematically shows a perspective view illustrating a preferred
embodiment of the combined sensor according to the present invention.
FIG. 16 schematically shows a perspective view illustrating another
preferred embodiment of the combined sensor according to the present
invention.
FIG. 17 schematically shows illustrative production steps for the vibration
gyro sensor according to the first embodiment shown in FIG. 1.
FIG. 18 schematically shows illustrative production steps for the vibration
gyro sensor according to the fifth embodiment shown in FIG. 7.
FIG. 19 shows a perspective view illustrating a magnified electrode
structure of the type based on the use of the longitudinal effect of the
electric field-induced strain.
FIG. 20 schematically shows a perspective view illustrating a thirteenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 21 schematically shows a perspective view illustrating a fourteenth
preferred embodiment of the vibration gyro sensor according to the present
Invention.
FIG. 22 schematically shows a perspective view illustrating a fifteenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 23 schematically shows a perspective view illustrating a sixteenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 24 schematically shows a perspective view illustrating an exemplary
structure of projections used to adjust the resonance frequency in the
vibration gyro sensor according to the fifteenth embodiment.
FIG. 25 schematically shows a perspective view illustrating another
exemplary structure of projections used to adjust the resonance frequency
in the vibration gyro sensor according to the fifteenth embodiment.
FIG. 26 schematically shows a perspective view illustrating a seventeenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 27 schematically shows a perspective view illustrating an exemplary
structure used to adjust the resonance frequencies for driving and
detection by changing spring constants of the driving and detecting
sections in the vibration gyro sensor according to the seventeenth
embodiment.
FIG. 28 schematically shows a perspective view illustrating an eighteenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 29 schematically shows a perspective view illustrating a nineteenth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 30 schematically shows a perspective view illustrating a twentieth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 31 schematically shows a perspective view illustrating a twenty-first
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 32 schematically shows a perspective view illustrating a twenty-second
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 33 schematically shows a perspective view illustrating a twenty-third
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 34 schematically shows a perspective view illustrating a twenty-fourth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 35 schematically shows a perspective view illustrating a twenty-fifth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 36 schematically shows a perspective view illustrating a twenty-sixth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 37 schematically shows a perspective view illustrating an exemplary
wiring formation pattern led from pairs of electrodes of
piezoelectric/electrostrictive elements in the vibration gyro sensor
according to the seventeenth embodiment.
FIG. 38 schematically shows a perspective view illustrating a
twenty-seventh preferred embodiment of the vibration gyro sensor according
to the present invention.
FIG. 39 schematically shows a perspective view illustrating a twenty-eighth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 40 schematically shows a perspective view illustrating a twenty-ninth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 41 schematically shows a perspective view illustrating a thirtieth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 42 schematically shows a perspective view illustrating a thirty-first
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 43 shows a cross-sectional view taken along a line A--A shown in FIG.
42.
FIG. 44 schematically shows a perspective view illustrating a thirty-second
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 45 schematically shows a perspective view illustrating a thirty-third
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 46 schematically shows a perspective view illustrating a thirty-fourth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 47 schematically shows a perspective view illustrating a thirty-fifth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 48 shows a cross-sectional view taken along a line B--B shown in FIG.
47.
FIG. 49 schematically shows a perspective view illustrating a thirty-sixth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 50 schematically shows a perspective view illustrating a
thirty-seventh preferred embodiment of the vibration gyro sensor according
to the present invention.
FIG. 51 schematically shows a perspective view illustrating a thirty-eighth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 52 schematically shows a perspective view illustrating a thirty-ninth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 53 shows characteristic curves illustrating the change in resonance
angular frequency ratio depending on the length of the support rod for
supporting the tuning fork.
FIG. 54 schematically shows a perspective view illustrating a fortieth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 55 schematically shows a perspective view illustrating a forty-first
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 56 schematically shows a perspective view illustrating a forty-second
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 57 schematically shows a perspective view illustrating a forty-third
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 58 schematically shows a perspective view illustrating a forty-fourth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 59 schematically shows a perspective view illustrating a forty-fifth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 60 schematically shows a perspective view illustrating a forty-sixth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 61 schematically shows a perspective view illustrating a forty-seventh
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 62 shows a magnified structure of a portion at which lead wires are
led in the vibration gyro sensor according to the forty-seventh
embodiment.
FIG. 63 schematically shows a perspective view illustrating a forty-eighth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 64 shows a magnified structure of a portion at which lead wires are
led in the vibration gyro sensor according to the forty-eighth embodiment.
FIG. 65 schematically shows a perspective view illustrating a forty-ninth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 66 schematically shows a perspective view illustrating a fiftieth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 67 schematically shows a perspective view illustrating a fifty-first
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 68 schematically shows a perspective view illustrating a fifty-second
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 69 schematically shows a perspective view illustrating a fifty-third
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 70A shows a cross-sectional view taken along a line C--C shown in FIG.
69.
FIG. 70B shows a cross-sectional view taken along a line D--D shown in FIG.
69.
FIG. 70C shows a cross-sectional view taken along a line E--E shown in FIG.
69.
FIG. 71 schematically shows a perspective view illustrating a fifty-fourth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 72 schematically shows a perspective view illustrating a fifty-fifth
preferred embodiment of the vibration gyro sensor according to the present
invention.
FIG. 73 schematically shows an exploded perspective view illustrating
another structure of the vibration gyro sensor according to the first
embodiment shown in FIG. 1.
FIG. 74 schematically shows an exploded perspective view illustrating the
vibration gyro sensor according to the thirty-third embodiment shown in
FIG. 45.
FIG. 75 schematically shows an exploded perspective view illustrating the
vibration gyro sensor according to the thirty-fourth embodiment shown in
FIG. 46.
FIG. 76 schematically shows an exploded perspective view illustrating the
vibration gyro sensor according to the thirty-fifth embodiment shown in
FIG. 47.
DETAILED DESCRIPTION
The features of the present invention will be described in detail below
with reference to various embodiments of the vibration gyro sensor
illustrated in the drawings in order to more specifically and clearly
describe the present invention.
At first, an embodiment (first embodiment) of the vibration gyro sensor
according to the present invention is shown in FIG. 1. In this embodiment,
two angular rod-shaped vibrators 2, 2 composed of a fired product of
ceramics, each of which has a rectangular cross section and extends
longitudinally, are arranged in parallel to one another and separated from
each other by a predetermined spacing distance. The two vibrators 2, 2 are
connected in an integrated manner at their proximal ends to a rectangular
angular rod-shaped support base 4 composed of a fired product of ceramics
respectively so that the vibrators 2, 2 are supported by the support base
4. Each of the vibrators 2, 2 includes a first plate-shaped section 6 to
serve as a detecting section which is formed in an integrated manner with
its thin-walled region disposed fairly close to the support base 4 and
with its principal surface extending in a direction of arrangement of the
vibrators 2, 2. Each of the vibrators 2, 2 has its proximal end region to
serve as a thin-walled second plate-shaped section 8 which has its width
thinner than a width of the vibrator 2 and has its principal surfaces
extending in a direction perpendicular to the first plate-shaped section
6. The vibrators 2, 2 are connected in an integrated manner to the support
base 4 via the second plate-shaped sections 8, 8. The two vibrators 2, 2
are connected to one another in an integrated manner at their regions
located between the first plate-shaped sections 6, 6 and the second
plate-shaped sections 8, 8 respectively via a third plate-shaped section
10 which is more thin-walled than the vibrators 2, 2 and has its principal
surface parallel to the principal surfaces of the first plate-shaped
sections 6, 6. Namely, the two vibrators 2, 2, the support base 4, the
first plate-shaped sections 6, 6, the second plate-shaped sections 8, 8,
and the third plate-shaped section 10 are constructed by an integrated
fired product made of ceramics, thus giving an integrated structure.
Namely, as shown in FIG. 2, the vibration gyro sensor, which is constructed
by the integrated fired product of ceramics as described above, can be
grasped as an integrated stacked structure comprising a thin plate layer
22, a substrate layer 24, and a spacer layer 26. Accordingly, the first
plate-shaped sections 6, 6 and the third plate-shaped section 10 are given
by the thin plate layer 22, while the vibrators 2, 2 and the second
plate-shaped sections 8, 8 are given by stacking and integrating the thin
plate layer 22 and the substrate layer 24. Further, the support base 4 is
given by stacking and integrating the thin plate layer 22, the substrate
layer 24, and the spacer layer 26.
Detecting piezoelectric/electrostrictive elements 12, 12 are formed in an
integrated manner on the thin-walled first plate-shaped sections 6, 6
formed on the respective vibrators 2, 2, in accordance with a known film
formation method respectively. As shown in FIG. 3 with magnification, the
detecting piezoelectric/electrostrictive element 12 is directly formed on
the first plate-shaped section 6 in a form in which a thin film-shaped
lower electrode 12a, a piezoelectric/electrostrictive layer 12b, and an
upper electrode 12c are stacked and integrated with each other. The
detecting piezoelectric/electrostrictive elements 12, 12 detect vibration
or displacement induced in the vibrators 2, 2 in a direction perpendicular
to the arrangement plane of the two vibrators 2, 2. A driving
piezoelectric/electrostrictive element 14 which serves as a driving means
is formed in an integrated manner on the third plate-shaped section 10,
and is constructed in the same manner as the detecting
piezoelectric/electrostrictive elements 12, 4 12, in accordance with the
known film formation method. When the driving
piezoelectric/electrostrictive element 14 is operated, the two vibrators
2, 2 are subjected to bending vibration in their arrangement plane in
mutually opposite directions, i.e., in directions to make mutual approach
and separation in the x axis direction.
Thin-walled excisable sections 16, 16 are provided at forward ends of the
respective vibrators 2, 2 on a side opposite to the connecting section
with respect to the support base 4, and the excisable sections 16, 16
extend in an integrated manner therefrom. The excisable sections 16, 16
may be easily trimmed by means of, for example, laser machining and
ultrasonic machining. The upper surface of the support base 4 is flush
with the upper surfaces of the vibrators 2, 2, and the support base 4 has
a shape with its thickness which is thicker than that of the vibrators 2,
2. Accordingly, the lower surface of the support base 4 is located at a
position lower than the vibrators 2, 2. Namely, the support base 4
includes, in an integrated manner, a spacer section 18 corresponding to
the spacer layer 26 shown in FIG. 2. The support base 4 is thicker than
the vibrators 2, 2 by a thickness of the spacer section 18. When the
vibration gyro sensor is attached at the portion of the support base 4 to
a flat attachment plane in the vertical direction by the aid of bolts 20,
the vibrators 2, 2 do not suffer interference from the attachment plane,
owing to the presence of the spacer section 18 as described above.
Therefore, the vibration gyro sensor having the structure as described
above is operated as follows. Namely, the third plate-shaped section 10
undergoes deformation by operating the driving
piezoelectric/electrostrictive element 14. Accordingly, the two vibrators
2, 2 are subjected to excited vibration (bending vibration) in mutually
opposite directions in the x axis direction, in other words. In directions
to make mutual approach and separation in the rectangular coordinate
system composed of the x, y, z axes shown in FIG. 1. In such a state, when
the rotational force about the z axis acts on the vibrators 2, 2, the
Coriolis force acts in the y axis direction on the vibrators 2, 2 on the
basis of the angular velocity about the z axis. Accordingly, the Coriolis
force allows the vibrators 2, 2 to make vibration in mutually opposite
directions in the y axis direction. The bending vibration of the vibrators
2, 2 in the y axis direction as described above is detected as an
electromotive force (voltage) by the aid of the detecting
piezoelectric/electrostrictive elements 12, 12.
As described above, the vibration gyro sensor is constructed as a whole by
the integrated fired product made of ceramics. Therefore, there is no
magnetic material such as the conventional elinvar alloy in the materials
for constructing the vibration gyro sensor. For this reason, no problem
occurs, i.e., the characteristics of the sensor are not affected by any
ambient magnetic field. The detecting piezoelectric/electrostrictive
elements_12, 12 and the driving piezoelectric/electrostrictive element 14
are directly formed in the integrated manner on the first plate-shaped
sections 6, 6 and the third plate-shaped section 10 in accordance with the
film formation method. No adhesive layer exists at all between the
elements and the plate-shaped sections. Therefore, the problem of
decreased in sensitivity, which would be otherwise caused by the
absorption of stress brought about by such an adhesive layer, is
effectively eliminated.
It is a matter of course that the deformation is advantageously caused by
the operation of the driving piezoelectric/electrostrictive element 14,
owing to the fact that the driving piezoelectric/electrostrictive element
14 to serve as an actuator is formed in the integrated manner on the
thin-walled third plate-shaped section 10. Further, the respective
vibrators 2, 2 are connected in the integrated manner to the support base
4 via the thin-walled second plate-shaped sections 8, 8, and the second
plate-shaped sections 8, 8 are provided as the thin plate sections having
their principal surfaces which extend in the direction (y axis direction)
perpendicular to the direction (x axis direction) of vibration of the
vibrators 2, 2. Accordingly, the rigidity in the direction of vibration is
effectively decreased, making it possible to easily cause vibration. Thus
large displacement is obtained by the driving operation effected on the
vibrators 2, 2 by the driving piezoelectric/electrostrictive element 14.
Especially, when the ratio of the width (thickness) to the height of the
second plate-shaped section 8 is made small, it is possible to suppress
vibration in the vertical direction (y axis direction) which serves as a
factor to decrease the sensitivity. Further, as for the region of
arrangement of the detecting piezoelectric/electrostrictive element 12,
the first plate-shaped section 6, on which the detecting
piezoelectric/electrostrictive element 12 is formed in the integrated
manner, is formed to be more thin-walled than the vibrator 2 so that its
principal surface extends in the direction of vibration (x axis direction)
of the vibrator 2. In other words, the principal surface is located within
the vibration plane of the vibrator 2. Accordingly, large displacement is
obtained when bending vibration is generated in the y axis direction which
is the direction perpendicular to the x axis direction.
As described above, the easily bendable regions exist in any of the
direction of detecting vibration (direction of the y axis) and the
direction of driving vibration (direction of the x axis), and hence large
displacement is obtained in any of the driving and detecting operations.
Accordingly, the sensitivity of the vibration gyro sensor is improved.
Especially, the first plate-shaped section 6, on which the detecting
piezoelectric/electrostrictive element 12 is formed for giving the
detecting section, is thin-walled to provide the structure so that the
stress is concentrated. Thus a large output is obtained.
In the embodiment described above, there is provided the thin-walled
excisable section 16 which extends in the integrated manner from the
forward end of the vibrator 2. Therefore, the excisable section 16 is
easily subjected to the trimming processing or machining such as the laser
machining and the ultrasonic machining, making it easy to adjust the
resonance frequency of the vibrator 2. The electrode area of the detecting
piezoelectric/electrostrictive element 12 and the driving
piezoelectric/electrostrictive element 14 can be easily changed by using a
laser or the like, making it possible to easily adjust the electric
characteristics thereof.
Further, the vibration gyro sensor according to this embodiment has the
structure in which the third plate-shaped section 10, on which the driving
piezoelectric/electrostrictive element 14 is provided, is formed in the
integrated manner so that the two vibrators 2, 2 are bridged at their
proximal ends. Accordingly, the vibration gyro sensor is also advantageous
in that it is possible to effectively suppress the restriction of
vibration of the vibrators 2, 2 by the third plate-shaped section 10.
The vibration gyro sensor according to the present invention may be
embodied by various structures other than the structure described above,
within a range without deviating from the gist or essential
characteristics of the present invention. Representative embodiments are
shown in FIG. 4 and following embodiments. The following embodiments will
be explained only for their characteristic portions. The same or
equivalent components or parts as those described in the first embodiment
are designated by the same reference numerals, detailed explanation of
which will be omitted.
A second embodiment shown in FIG. 4 has the following feature. Namely,
vibrators 2, 2 are connected in an integrated manner to forward ends of
U-shaped portions of a U-shaped support base 4 via thin-walled first
plate-shaped sections 6, 6. Second plate-shaped sections 8, 8 are
positioned at forward ends of the vibrators 2, 2. A thin-walled third
plate-shaped section 10 for connecting the two vibrators 2, 2 in an
integrated manner is formed in an integrated manner at positions located
nearer to the forward ends as compared with the second plate-shaped
sections 8, 8.
In the second embodiment, the third plate-shaped section 10 is provided at
the position nearer to the forward ends of the vibrators 2, 2 as compared
with the first embodiment. Therefore, although a problem arises in that
the vibration of the vibrators 2, 2 tends to be restricted by the third
plate-shaped section 10, it is still possible to obtain displacement which
is larger than that obtained by the conventional vibration gyro sensor.
Third and fourth embodiments shown in FIGS. 5 and 6 respectively have the
following feature as compared with the first and second embodiments
described above. Namely, the vibration gyro sensor is constructed by an
integrated fired product made of ceramics having a structure in which an
angular bar-shaped support bar 28, having a rectangular cross section, is
arranged between two vibrators 2, 2 in parallel to the vibrators 2, 2.
Namely, the support bar 28 is disposed between the two vibrators 2, 2 at a
position separated from the vibrators 2, 2 by a predetermined distance,
and it is integrally connected to and supported by a support base 4.
Thin-walled third plate-shaped sections 10, 10 are formed in an integrated
manner between the support bar 28 and the vibrators 2, 2 disposed at the
right and left thereof. Driving piezoelectric/electrostrictive elements
14, 14 are formed on the third plate-shaped sections 10, 10 respectively.
The operation of the driving piezoelectric/electrostrictive elements 14,
14 causes the right and left vibrators 2, 2 to vibrate in mutually
opposite directions respectively.
FIGS. 7 and 8 show fifth and sixth embodiments having the following
structure respectively. Namely, an integrated fired structure of ceramics
is used in a state in which the support base 4 for supporting two
vibrators 2, 2 at their proximal ends is constructed by an attachment
frame 30 having a rectangular configuration. The two vibrators 2, 2 are
accommodated in the attachment frame 30, and predetermined gaps are formed
between the vibrators 2, 2 and the attachment frame 30.
Independent driving means (actuators) are provided in an integrated manner
between the two vibrators 2, 2 and the attachment frame 30 which surrounds
the two vibrators 2, 2 respectively. Namely, thin-walled third
plate-shaped sections 10, 10 are formed in an integrated manner between
the two vibrators 2, 2 and sides of the attachment frame 30 opposing
thereto. Driving piezoelectric/electrostrictive elements 14, 14 are formed
on the third plate-shaped sections 10, 10 respectively in accordance with
the film formation method.
In the vibration gyro sensor having the structure as described above, the
attachment frame 30 can be tightly fixed to a flat attachment plane via
the spacer section 18 by the aid of bolts 20 or the like. Accordingly, the
vibration gyro sensor is advantageous in that the degree of freedom is
large concerning the place for installation.
Seventh and eighth embodiments shown in FIGS. 9 and 10 have similar
structures as those described in the first and second embodiments
concerning the support base 4. However, the support base 4 is provided as
an integrated fired structure made of ceramics in a form of an attachment
frame 30 having a rectangular configuration so that the two vibrators 2, 2
are surrounded thereby.
Namely, each of the vibration gyro sensors according to the seventh and
eighth embodiments includes a driving means 10, 14 formed in an integrated
manner between the two vibrators 2, 2 arranged in the attachment frame 30
having the rectangular frame structure. In these embodiments, the
attachment frame 30 can be tightly fixed via the spacer section 18 in the
same manner as described in the fifth and sixth embodiments. These
embodiments are also advantageous in that the degree of freedom is large
concerning the place for installation.
FIG. 11 shows a ninth embodiment of the vibration gyro sensor according to
the present invention. The vibration gyro sensor is constructed by an
integrated fired product structure made of ceramics wherein a frame 32
having a rectangular configuration, which serves as a support base for
supporting two vibrators 2, 2 at their proximal ends, is provided so that
the two vibrators 2, 2 are surrounded thereby. A thin-walled second
plate-shaped section 8, which is provided to lower the rigidity of the
vibrators 2, 2 in the direction of vibration and facilitate vibration, is
formed in an integrated manner at a portion of the frame 32 located
between support regions for the two vibrators 2, 2 so that the second
plate-shaped section 8 gives its principal surface extending in a
direction perpendicular to the direction of vibration (arrangement plane
for the vibrators 2, 2). A third plate-shaped section 10, which is more
thin-walled than the frame 32, is formed at a portion of the frame 32
opposing to the region for forming the second plate-shaped section 8 so
that the third plate-shaped section 10 has its principal surface parallel
to the principal surfaces of the first plate-shaped sections 6, 6. A
driving piezoelectric/electrostrictive element 14 is formed in an
integrated manner on the third plate-shaped section 10 in accordance with
the film formation method.
Therefore, in the vibration gyro sensor having the structure as described
above, the operation of the driving piezoelectric/electrostrictive element
14 causes deformation of the third plate-shaped section 10 which induces
bending vibration in the frame 32 by using the region of the second
plate-shaped section 8 as a center. On the basis of the bending vibration,
the two vibrators 2, 2 are vibrated in an excited manner.
FIGS. 12 and 13 show tenth and eleventh embodiments respectively, each
based on the use of an integrated fired product structure made of
ceramics, as illustrative structures for facilitating fixation of the
vibration gyro sensor shown in FIG. 11.
Of the tenth and eleventh embodiments, the embodiment shown in FIG. 12
includes an attachment section 34 for fixing a frame 32, which is provided
in an integrated manner at an outer surface corresponding to a region for
forming the second plate-shaped section 8 formed in the rectangular frame
32. Specifically, the attachment section 34 has a triangular
configuration, and it is connected in an integrated manner to the outer
surface of the second plate-shaped section 8 at an apex of the triangle.
The connecting section, at which the attachment section 34 is connected to
the second plate-shaped section 8, has a width (length in the lateral
direction in FIG. 12) which is smaller than a width of the second
plate-shaped section 8 (length in the lateral direction in FIG. 12). This
is done since it is desirable to suppress, as small as possible, the
restriction on the deformation of the second plate-shaped section 8, which
would be caused by the connection of the attachment section 34. The
vibration gyro sensor is fixed such that the attachment section 34 is
fixed via the spacer section 18 by the aid of bolts 20 or the like.
The embodiment shown in FIG. 13 illustrates a modified embodiment of the
attachment section 34 as described in the embodiment shown in FIG. 12.
Namely, this embodiment has a structure including, in an integrated
manner, an attachment frame 36 which is disposed outside the frame 32 and
separated therefrom by predetermined distances so that the frame 32 for
giving the vibration gyro sensor is surrounded. A tight fixing structure
can be realized by fixing the attachment frame 36 having a rectangular
frame configuration by using bolts 20.
A twelfth embodiment of the vibration gyro sensor according to the present
invention is shown in FIG. 14, based on the use of an integrated fired
product structure made of ceramics. In this embodiment, a support base 4,
which is provided for supporting two vibrators 2, 2 at their proximal
ends, has an angular U-shaped configuration. A second plate-shaped section
8 is formed at a portion located between support regions of the support
base 4 for the two vibrators 2, 2. An attachment section 34 for fixing the
support base 4 is connected in an integrated manner to the outer surface
of the second plate-shaped section 8, in the same manner as the embodiment
shown in FIG. 13. An attachment frame 36 having a rectangular frame
configuration, which is formed in an integrated manner together with the
attachment section 34, is disposed outside the two vibrators 2, 2 and the
support base 4, and separated by predetermined distances therefrom so that
the two vibrators 2, 2 and the support base 4 are surrounded thereby.
Third plate-shaped sections 10, 10, which are more thin-walled than the
attachment frame 36 and the support base 4, are formed in an integrated
manner with their principal surfaces parallel to principal surfaces of
first plate-shaped sections 6, 6 so that the third plate-shaped sections
10, 10 bridge the attachment frame 36 and portions of the support base 4
located on both sides of the second plate-shaped section 8, respectively.
Driving piezoelectric/electrostrictive elements 14, 14 are formed in an
integrated manner on the third plate-shaped sections 10, 10 in accordance
with the film formation method.
In the vibration gyro sensor having the structure as described above, the
portions of the support base 4 located on the both sides of the second
plate-shaped section 8 are vibrated by the operation of the driving
piezoelectric/electrostrictive elements 14, 14 as the driving means
provided between the attachment section 36 and the portions of the support
base 4. In turn, this causes, the vibrators 2, 2, to vibrate.
The use of the structure of the vibration gyro sensor according to the
present invention as described above makes it possible to easily realize
combination with other sensors. Specifically, the attachment frames 30, 36
shown in FIGS. 7 to 10 and FIGS. 13 and 14 may be utilized to provide a
second attachment frame which is adjacent to the attachment frame and
integrated with the attachment frame, as an integrated fired product
structure made of ceramics. Another sensor, which has a function different
from that of the vibration gyro sensor, is supported in an integrated
manner in the second attachment frame. Thus it is possible to provide a
combined sensor. An illustrative embodiment of such a combined sensor is
shown in FIG. 15.
In a combined sensor illustrated in FIG. 15, a second attachment frame 38
integrated with an attachment frame 36 is provided as an integrated fired
product structure made of ceramics, the second attachment frame 38 being
adjacent to the attachment frame 36 of the vibration gyro sensor as shown
in FIG. 13. An acceleration sensor, which has a function distinct from the
vibration gyro sensor, is provided in an integrated manner in the second
attachment frame 38. In FIG. 15, an acceleration sensor section 40 for
detecting the angular velocity around the z axis, which constructs the
vibration gyro sensor, is provided on the left side of the system. An
acceleration sensor section 42 is formed in the second attachment frame 38
on the right side of the system. Namely, the acceleration sensor section
42 comprises a first sensor 44A and a second sensor 44B for detecting the
acceleration in the y axis direction, and a third sensor 44C and a fourth
sensor 44D for detecting the acceleration in the x axis direction.
Each of the first and second sensors 44A, 44B comprises a vibrator 46a, 46b
as an inertial mass, a thin plate-shaped detecting section 48a, 48b for
connecting the vibrator 46a, 46b to the attachment frame 38 in an
integrated manner, and a detecting piezoelectric/electrostrictive element
50a, 50b formed on the detecting section 48a, 48b in an integrated manner
in accordance with the film formation method and having the same or
equivalent structure as that of the detecting
piezoelectric/electrostrictive element 14 described above. Therefore, when
an acceleration in the y axis direction is inputted, the detecting
sections 48a, 48b are deformed respectively. A predetermined electromotive
force (voltage) is outputted from the detecting
piezoelectric/electrostrictive elements 50a, 50b on the basis of the
deformation. The first and'second sensors 44A, 44B also detect the
acceleration in the x axis direction. When they are operated as described
above, the two sensors make deformation in mutually opposite directions,
the displacement being different from the displacement in an identical
direction brought about when the acceleration in the y axis direction is
applied. Accordingly, it is possible to achieve signal separation.
Each of the third and fourth sensors 44C, 44D also comprises a vibrator
46c, 46d as an inertial mass, a thin plate-shaped detecting section 48c,
48d for connecting the vibrator 46c, 46d to the attachment frame 38 in an
integrated manner, a detecting piezoelectric/electrostrictive element 50c,
50d formed on the detecting section 48c, 48d in an integrated manner in
accordance with the film formation method and having the same or
equivalent structure as that of the detecting
piezoelectric/electrostrictive element 12 described above, and a thin
plate-shaped connecting section 46c', 46d' for connecting the vibrator
46c, 46d to the attachment frame 38 to support the vibrator 46c, 46d in a
state in which the vibrator 46c, 46d is easily displaceable in the x axis
direction. Therefore, when an acceleration in the x axis direction is
inputted, a predetermined electromotive force (voltage) is outputted from
the detecting piezoelectric/electrostrictive elements 50c, 50d on the
basis of deformation of the two detecting sections 48c, 48d.
FIG. 16 shows another embodiment of the combined sensor having a different
structure. A combined sensor disclosed in FIG. 16 has an integrated fired
product structure made of ceramics in which an angular velocity sensor
section 40 and an acceleration sensor section 42 are provided in an
integrated manner, in the same manner as the combined sensor illustrated
in FIG. 15. However, this embodiment is different from the foregoing
embodiment in the structures of the first and second sensors 44A, 44B.
Namely, a connecting section 46a', 46b', which is provided for connecting,
in an integrated manner, a vibrator 46a, 46b as an inertial mass of first
and second sensors 44A, 44B to an attachment frame 38 respectively, is
formed to have a thin plate configuration which is easily deformed in the
z axis direction. Therefore, when an acceleration in the z axis direction
is inputted, the vibrators 46a, 46b as the inertial masses give large
displacement owing to the presence of the connecting sections 46a', 46b'
to be easily deformed, on the basis of which a predetermined electromotive
force (voltage) is outputted by the detecting
piezoelectric/electrostrictive elements 50a, 50b.
Any of the vibration gyro sensors and the combined sensors according to the
present invention is composed of the integrated fired product made of
ceramics except for the piezoelectric/electrostrictive elements 12, 14 and
50a to 50d. Specifically, they are produced as follows.
At first, in the present invention, the main sensor body, which comprises,
for example, the vibrators 2, the support base 4, the first to third
plate-shaped sections 6, 8, 10, and the spacer section 18, is given by the
integrated fired product made of ceramics. Those usable, without any
problem, as materials for forming the integrated fired product of ceramics
for providing the main sensor body include any of ceramic materials
composed of oxide and any of ceramic materials composed of those other
than oxide, provided that the material is an insulative material or a
dielectric material having large mechanical strength, which can be
subjected to a heat treatment at about 1400.degree. C. as described later
on, and which can be stacked and integrated with the
piezoelectric/electrostrictive elements 12, 14 and other components
without using any adhesive or the like. Especially, those preferably
adopted include materials comprising a major component of at least any one
of aluminum oxide, magnesium oxide, zirconium oxide, aluminum nitride, and
silicon nitride, in order to obtain excellent operation characteristics,
i.e., large displacement, large generated force, and quick response speed.
In particular, it is recommended to use ceramic materials comprising, as a
major component or major components, aluminum oxide and/or zirconium
oxide. More specifically, those advantageously used include materials
comprising a major component of zirconium oxide stabilized with at least
one compound selected from the group consisting of yttrium oxide,
ytterbium oxide, cerium oxide, calcium oxide, and magnesium oxide, because
they exhibit features such as high toughness and high mechanical strength
obtained even when the plate thickness is thin.
In order to stabilize zirconium oxide, the foregoing compound is preferably
added in an amount of 1 mole % to 30 mole % in the case of yttrium oxide
and ytterbium oxide, 6 mole % to 50 mole % in the case of cerium oxide, or
5 mole % to 40 mole % in the case of calcium oxide and magnesium oxide.
Especially, it is desirable to use yttrium oxide as a stabilizer. In this
case, yttrium oxide is desirably added in an amount of 1.5 mole % to 6
mole %, more preferably 2 mole % to 4 mole %. When yttrium oxide is added
to zirconium oxide in the foregoing range of addition, the crystal phase
is partially stabilized, thus giving excellent characteristics for the
main sensor body.
When stabilized or partially stabilized zirconia is used for the thin plate
layer, it is preferable to contain an auxiliary shown in the following
table. An equivalent effect can be obtained even when the
piezoelectric/electrostrictive element contains the following auxiliary.
TABLE
______________________________________
Type of
Preferable More applicable
content preferable electric
range range field-induced
Auxiliary
(% by weight)
(% by weight)
Effect
strain
______________________________________
alumina
0.1 .about. 5.0
0.2 .about. 2.0
*1 lateral effect
titania
0.1 .about. 5.0
0.2 .about. 2.0
*2 longitudinal effect
______________________________________
*1: Stress itself or dispersion of stress of the piezoelectric layer is
reduced by avoiding conglutination (fusion) of the thin plate layer and
the piezoelectric layer.
*2: Sufficient joining is ensured between the thin plate layer and the
piezoelectric layer to obtain high reliability.
As shown in FIG. 2, the integrated fired product of ceramics, which
constructs the main sensor body as described above, advantageously
comprises the thin plate layer 22, the substrate layer 24, and the spacer
layer 26, if necessary. It is advantageous to contain silicon oxide (SiO,
SiO.sub.2) at least in the material to give the thin plate layer 22. The
content of silicon oxide is preferably not less than 0.5% by weight and
not more than 5% by weight, and especially desirably not less than 1% by
weight and not more than 3% by weight. The content of silicon oxide in the
ratio as described above is effective to avoid any excessive reaction with
the piezoelectric/electrostrictive material during the heat treatment for
the piezoelectric/electrostrictive element 12, 14 formed on the thin plate
layer 22 so that good actuator characteristics or detection
characteristics may be obtained.
Further, in order to obtain quick response and large displacement in the
vibration gyro sensor and the combined sensor including the same according
to the present invention, the thickness of the thin plate layer 22 on
which the piezoelectric/electrostrictive elements are formed in the
integrated manner, i.e., the thickness of the first plate-shaped section 6
and the third plate-shaped section 10 is generally not more than 50 .mu.m,
preferably not more than 30 .mu.m, and more preferably not more than 15
.mu.pm. On the other hand, the thickness of the substrate layer 24 is
appropriately determined. However, the thickness of the substrate layer 24
is generally not less than 30 .mu.m, preferably not less than 50 .mu.m,
and more preferably not less than 100 .mu.m. In order to obtain large
displacement and large generated force in the actuator or the detecting
section, at least the thin plate layer 22 preferably has an average
particle diameter of crystals of 0.1 to 2 .mu.m. More preferably, the thin
plate layer 22 is desirably composed of a ceramic material having an
average particle diameter of not more than 1 .mu.m.
Those usable to obtain the integrated fired product of ceramics to give the
main sensor body comprising the thin plate layer 22 and the substrate
layer 24 (and the spacer layer 26) as described above include, for
example, a green sheet stacking method for stacking, in a state of green
sheets, the thin plate layer 22, the substrate layer 24, and the spacer
layer 26, as well as various molding methods based on the use of a mold,
such as pressure molding, casting molding, and injection molding, and
processing or machining methods for forming, for example, the vibrator 2,
the support base 4, and the first to third plate-shaped sections 6, 8, 10
by means of machining processing such as ultrasonic, cutting, and grinding
processing methods. Especially, it is preferable to use the green sheet
stacking method since no processing stress remains, and the accuracy for
the thickness of the thin plate layer 22 is high. The green sheet stacking
method is preferably based on the use of first, second, and third green
sheets for providing the thin plate layer 22, the substrate layer 24, and
the spacer layer 26, respectively. A method is adopted, in which the
first, second, and third green sheets are stacked by means of thermal
adhesion under pressure, and then they are integrated with each other by
firing. It is preferable to use, as the first to third green sheets, green
sheets which at least have the same degree and percentage of contraction,
upon firing integration.
The green sheet stacking method as described above specifically includes
the following three methods. In the first method, the first to third green
sheets are formed to have shapes corresponding to the thin plate layer 22,
the substrate layer 24, and the spacer layer 26 shown in FIG. 2,
respectively. They are stacked and integrated with each other, followed by
firing, to produce an integrated fired product. After that, the
piezoelectric/electrostrictive elements 12, 14 are formed in an integrated
manner at predetermined regions on the thin plate layer 22 in accordance
with the film formation method. In the second method, the first green
sheet, to which the shape of the thin plate layer 22 is not given, is
stacked and integrated with the second and third green sheets having
shapes corresponding to the substrate layer 24 and the spacer layer 26,
and they are fired to obtain an integrated fired product. After that, the
shape of the thin plate layer 22 is realized by means of, for example,
laser machining and ultrasonic machining, and then the
piezoelectric/electrostrictive elements are formed in an integrated manner
at predetermined regions on the thin plate layer 22. In the third method,
the first green sheet, to which the shape of the thin plate layer 22 is
not given, is used. The first green sheet is stacked and integrated with
the second and third green sheets having shapes corresponding to the
substrate layer 24 and the spacer layer 26, followed by firing to produce
an integrated fired product. Piezoelectric/electrostrictive elements are
formed in an integrated manner at predetermined regions of fired product
portions of the first green sheet. After that, the shape of the thin plate
layer 22 is realized by means of, for example, laser machining and
ultrasonic machining. Thus the objective vibration gyro sensor is
obtained. Especially, the present invention advantageously adopts the
last-mentioned third method in order to avoid deformation which would be
caused by the heat treatment during formation of the
piezoelectric/electrostrictive elements. The shapes of the thin plate
layer 22, the substrate layer 24, and the spacer layer 26 are preferably
realized by using the method in which the green sheets are shaped to give
such shapes, or by adopting, for example, laser machining, press working
with a mold, and ultrasonic machining. Especially, the press working with
a mold is advantageously used, because this method is excellent in mass
production performance and integration performance.
FIG. 17 shows an example of the desirable production technique (third
method) for the vibration gyro sensor in accordance with the green sheet
stacking method as described above. In this procedure, a first green sheet
52 for giving the thin plate layer 22 is not processed into the shape of
the thin plate layer 22 at all. The first green sheet 52 is merely used as
one thin plate having a rectangular configuration. A second green sheet 54
for giving the substrate layer 24 is processed into the shape
corresponding to the shape of the substrate layer 24. A third green sheet
56 for giving the spacer layer 26 is also processed into the shape
corresponding to the shape of the spacer layer 26. The first, second, and
third green sheets 52, 54, 56 are stacked, and then they are fired and
integrated into one unit. After that, the piezoelectric/electrostrictive
elements 12, 14 are formed in an integrated manner on the predetermined
regions on the thin plate layer 22 of the obtained fired product 58 in
accordance with the film formation method as described later on.
Subsequently, cutting processing is applied to portions of the thin plate
layer 22 of the integrated fired product 58 by means of, for example,
laser machining or ultrasonic machining. Thus the vibration gyro sensor as
shown in FIG. 1 is completed.
In the case of the second method based on the green sheet stacking method
described above, the order of the step of forming the
piezoelectric/electrostrictive elements 12, 14 and the step of processing
the thin plate layer 22 is inverted, and the
piezoelectric/electrostrictive elements 12, 14 are formed in an integrated
manner. Thus the vibration gyro sensor as shown in FIG. 1 is completed.
In the green sheet stacking method in which the vibration gyro sensor is
obtained by stacking the first, second, and third green sheets 52, 54, 56
as described above, it is extremely easy to form the thin plate-shaped
excisable section 16 extending from the forward end of the vibrator 2 by
considering the shape of the thin plate layer 22. After the vibration gyro
sensor is produced, the resonance frequency is measured, and the excisable
section 16 formed at the forward end of the vibrator 2 is cut (excised) by
means of, for example, laser machining and ultrasonic machining, if
necessary. Thus the resonant frequency can be finely adjusted with ease.
As clarified from FIGS. 2 and 17, the vibration gyro sensor shown in FIG. 1
is constructed such that the second green sheet 54 for giving the
substrate layer 24 has a discontinuous structure of a form in which the
portions for giving the vibrators 2, 2 are separated, because the first
plate-shaped sections 6, 6 are formed by the thin plate layer 22 which is
given by the first green sheet 52. For this reason, it is difficult to
position such discontinuous sections. Further, there is an implicit
problem that deformation tends to occur during the firing and the heat
treatment performed when the piezoelectric/electrostrictive elements are
formed. Therefore, a technique is preferably adopted, in which a
continuous green sheet is prepared and used during stacking, and
discontinuous sections as described above are formed after completion of
the stacking and integration or the firing and integration. An example of
such a technique is shown in FIG. 18.
Namely, FIG. 18 shows one of effective techniques to produce the vibration
gyro sensor shown in FIG. 7. In this procedure, a second green sheet 54
for giving the substrate layer 24 is provided as a continuous sheet as
shown in FIG. 18. Namely, sections 58, 58 for forming the vibrators 2, 2
are connected via connecting sections 62, 62 to a section 60 for forming
the attachment frame 30, and thus the second green sheet 54 is used in a
state including no discontinuous portion. The second green sheet 54 is
stacked together with a first green sheet 52 and a third green sheet 56,
and they are fired and integrated with each other. After that, the
piezoelectric/electrostrictive elements 12, 14 are formed in an integrated
manner thereon, followed by performing machining for the thin plate layer
22 given by the first green sheet 52. Simultaneously with the machining,
or before or after the machining, the connecting sections 62, 62, which
connect the vibrators 2, 2 and the attachment frame 30, are cut by means
of, for example, laser machining or ultrasonic machining to cause
separation from the attachment frame 30. When cut sections 64, 64 are
formed from the connecting sections 62, 62, the vibrators 2, 2 are
released from restriction by the attachment frame 30. Thus the vibration
gyro sensor shown in FIG. 7 is completed.
The structure, in which any discontinuous section does not exist in the
second green sheet 54 as described above, may be realized not only for the
sensors having the structure which include the attachment frame 30, 36, 38
and the frame 32 so that the vibrators 2, 2 are surrounded as shown in
FIGS. 7 to 16, but also for the sensors having the structure including the
support bar 28 provided between the two vibrators 2, 2 as shown in FIGS. 5
and 6 such that connecting sections 62, 62 are formed between the
vibrators 2, 2 and the support bar 28, and they are finally cut at the cut
sections 64, 64.
In the production steps for the vibration gyro sensors and the combined
sensors described above, the piezoelectric/electrostrictive elements 12,
14 are formed on the predetermined regions on the thin plate layer 22 as
follows.
At first, in order to form the electrode films 12a, 12c and the
piezoelectric/electrostrictive film 12b composed of respective materials
on the predetermined regions on the thin plate layer 22, it is possible to
appropriately adopt various known film formation methods including, for
example, thick film methods such as screen printing, application methods
such as dipping, and thin film methods such as ion beam, sputtering,
vacuum vapor deposition, ion plating, CVD, and plating. However, there is
no limitation thereto at all. In order to form the
piezoelectric/electrostrictive film 12b, it is preferable to adopt
techniques based on, for example, screen printing, dipping, and
application. In these techniques, the film can be formed on the thin plate
layer 22 by using a paste or a slurry comprising, as a major component,
piezoelectric/electrostrictive ceramic particles, in which good operation
characteristics can be obtained. When the piezoelectric/electrostrictive
element 12, 14 is formed in accordance with the film formation method
described above, the element can be integrated with the thin plate layer
22 without using any adhesive. Accordingly, the use of the film formation
method is especially preferred because the reliability and the
reproducibility are excellent, and it is easy to achieve integration. The
shape of such a film is formed by means of pattern formation by using, for
example, the screen printing method and the photolithography method.
Alternatively, the pattern may be formed by removing unnecessary portions
by using mechanical processing methods such as laser processing, slicing,
and ultrasonic processing.
The shape of the film and the structure of the
piezoelectric/electrostrictive element 12, 14 formed integrally on the
predetermined region on the thin plate layer 22 in accordance with the
film formation method are not limited at all, to which those hitherto
known may be appropriately adopted. For example, other than the structure
based on the use of the lateral effect of the electric field-induced
strain as shown in FIG. 3, it is possible to appropriately adopt those
having a structure based on the use of the longitudinal effect of the
electric field-induced strain. No problem occurs concerning the shape of
the film. The shape of the film may be any of polygonal configurations
such as triangles and rectangles, circular configurations such as circles,
ellipses, and rings, comb-shaped configurations, lattice-shaped
configurations, and special configurations obtained by combining the
foregoing configurations.
The respective films 12a, 12b, 12c, which are formed on the first and third
plate-shaped sections 6, 10 given by the thin plate layer 22, may be
heat-treated every time when each film is formed so that the integrated
structure is established together with the respective plate-shaped
sections. Alternatively, all of the films may be formed, and then they may
be simultaneously heat-treated so that the respective films may be
simultaneously joined with the plate-shaped section in an integrated
manner. Incidentally, when the electrode film is formed by means of the
thin film formation technique, the heat treatment is not necessarily
indispensable to achieve integration in some cases.
As for the heat treatment temperature to integrate the films formed as
described above and the plate-shaped section, a temperature of about
800.degree. C. to 1400.degree. C. is generally adopted, and preferably, a
temperature within a range of 1000.degree. C. to 1400.degree. C. is
advantageously selected. When the piezoelectric/electrostrictive film 12b
is heat-treated, it is preferable to perform the heat treatment while
controlling the atmosphere by using an evaporation source composed of a
piezoelectric/electrostrictive material together so that the composition
of the piezoelectric/electrostrictive film is not unstable at a high
temperature.
The material for the electrode films 12a, 12c for constructing the
piezoelectric/electrostrictive element, produced in accordance with the
foregoing method, is not specifically limited, provided that the material
is a conductor which can withstand the oxidizable atmosphere at a high
temperature such as the heat treatment temperature and the firing
temperature. For example, the material may be a simple substance such as a
metal or an alloy, or the material may be a mixture of a metal or an alloy
and an additive such as an insulative ceramic and glass. Further, no
problem occurs when the material is a conductive ceramic. More
appropriately, it is preferable to use electrode materials comprising
major components of high melting point noble metals such as platinum,
palladium, and rhodium, and alloys such as silver-palladium,
silver-platinum, and platinum-palladium.
As for the mixture described above, it is desirable to use, as the ceramic
to be added to the metal and the alloy, the same material as the material
for constructing the first plate-shaped section and the third plate-shaped
section or the piezoelectric/electrostrictive material described later on.
The same material as the material for the plate-shaped section is
preferably added in an amount of 5 to 30% by volume. The same material as
the piezoelectric/electrostrictive material is preferably added in an
amount of about 5 to 20% by volume. Especially, the mixture, which is
obtained by mixing the metal or the alloy described above with the
material for constructing the plate-shaped section and the
piezoelectric/electrostrictive material, is advantageously used to form
the objective electrode.
The electrodes 12a, 12c, which are formed by using the material as
described above, are allowed to have appropriate thicknesses depending on
the use or application. As shown in FIG. 3, in the case of the type based
on the use of the lateral effect of the electric field-induced strain, the
electrode is generally formed to have a thickness of not more than 15
.mu.m, and preferably not more than 5 .mu.m. As shown in FIG. 19, in the
case of the type based on the use of the longitudinal effect of the
electric field-induced strain, the electrode is appropriately formed to
have a thickness of not less than 3 .mu.m, preferably not less than 10
.mu.m, and more preferably not less than 20 .mu.m.
Any material may be used as the piezoelectric/electrostrictive material to
give the film-shaped piezoelectric/electrostrictive layer 12b for
constructing the piezoelectric/electrostrictive elements 12, 14, provided
that the material exhibits the electric field-induced strain such as the
piezoelectric or electrostrictive effect. The material may be crystalline
materials, or amorphous materials. No problem occurs when the material is
any of semiconductor materials, dielectric ceramic materials, or
ferroelectric ceramic materials. The material may be materials which
require the polarization treatment, or materials which do not require the
polarization treatment.
Specifically, those preferably used as the piezoelectric/electrostrictive
material employed in the present invention include, for example, materials
comprising a major component of lead zirconate titanate (PZT system),
materials comprising a major component of lead magnesium niobate (PMN
system), materials comprising a major component of lead nickel niobate
(PNN system), materials comprising a major component of lead zinc niobate,
materials comprising a major component of lead manganese niobate,
materials comprising a major component of lead antimony stannate,
materials comprising a major component of lead titanate, materials
comprising a major component of barium titanate, and composite materials
thereof. No problem occurs when the material comprising the major
component of the PZT system is appropriately added with predetermined
additives to give materials, for example, those of the PLZT system
containing, as additives, oxides of lanthanum, barium, niobium, zinc,
nickel, and manganese, or other types of compounds thereof.
It is desirable that the thickness of the piezoelectric/electrostrictive
element 12, 14 constructed as described above is generally not more than
100 .mu.m, preferably not more than 50 .mu.m, and more preferably not more
than 30 .mu.m.
The present invention has been specifically described above on the basis of
the several embodiments. However, the present invention should not be
interpreted at all as one which is limited by the foregoing embodiments.
It should be understood that various changes, modifications, and
improvements may be added to the present invention on the basis of the
knowledge of those skilled in the art without deviating from the scope of
the present invention.
For example, in the illustrative respective embodiments, the spacer section
18 is provided, for example, for the support base 4, the attachment frame
30, 36, or the attachment section 34 so that the respective vibrators 2, 2
do not interfere with the attachment plane even when the vibrators 2, 2
makes vibration for detection. However, in some cases, it is unnecessary
to provide such a spacer section 18 depending on the shape or the
structure of the attachment plane.
In the illustrative embodiments, for example, the support base 4, the
attachment frame 30, 36, or the attachment section 34 is fixed by using
the bolts. However, it is also effective to glue and fix such components
by using an adhesive. In this case, it is preferable to fix the entire
lower surface of the spacer section 18 by using an adhesive. Those usable
as the adhesive include, for example, those of the epoxy resin type, the
acrylic resin type, the synthetic rubber type, the hot melt type, the
cyanoacrylate type, and the polyurethane resin type.
In the illustrative vibration gyro sensor according to the present
invention, the first plate-shaped section 6, on which the detecting
piezoelectric/electrostrictive element 12 is formed in the integrated
manner, is provided at the intermediate portion or the proximal end of the
vibrator 2. However, as shown in FIGS. 20 and 21, it is possible to
provide the first plate-shaped section 6 at the forward end of the
vibrator 2 to give an integrated structure continued to the excisable
section 16. In this case, the Coriolis force applied to the detecting
piezoelectric/electrostrictive element 12 is lowered, and the sensitivity
is decreased. However, this structure has a feature that it is
advantageous concerning achievement of a compact size and concerning
breakage.
Next, a fifteenth embodiment of the vibration gyro sensor according to the
present invention will be described with reference to FIG. 22.
The vibration gyro sensor according to the fifteenth embodiment comprises a
rectangular parallelepiped-shaped support base 100 with its longitudinal
direction extending in a certain direction (X direction in FIG. 22), two
vibrators 102A, 102B provided on one side surface of the support base 100
and having their direction of major axes extending in a direction (Y
direction in FIG. 22) perpendicular to the certain direction, two
vibrators 102C, 102D provided on another side surface of the support base
100 and having their direction of major axes extending in the Y direction,
and a frame 104 having its frame surface parallel to a plane including the
X and Y directions, for surrounding the support base 100 and the four
vibrators 102A to 102D.
The respective two vibrators 102A, 102B and 102C, 102D are supported by the
support base 100 at the respective side surfaces so that they extend in
parallel to one another while giving a predetermined spacing width "d".
Each of the vibrators 102A to 102D has a rectangular parallelepiped-shaped
main vibrator body 106, and a thin-walled plate-shaped connecting section
(second plate-shaped section) 108 for connecting the main vibrator body
106 to the support base 100. The connecting section 108 extends from a
central portion in the widthwise direction of an end surface of the main
vibrator body 106 on the side of the support base 100 to the support base
100. The height of the connecting section 108 is approximately the same as
that of the main vibrator body 106, and the width thereof is designed to
be smaller than the width of the main vibrator body 106, in the same
manner as described in the first embodiment (see FIG. 1).
An opening 110, which has an approximately rectangular planar
configuration, is formed through the frame 104 at its central portion. The
opening 110 penetrates through the frame 104 in its direction of height,
and it has an opening area of a degree to make it possible to surround the
support base 100 and the four vibrators 102A to 102D. The opening 110 has
rectangular cutouts 112 at portions corresponding to both longitudinal
ends of the support base 100. The distance between bottoms of the
respective cutouts 112 is designed to be longer than the length of the
support base 100 in the longitudinal direction. Side surfaces of the
respective cutouts 112 are opposed, at portions near to the opening 110,
to the side surfaces of the support base 100. Namely, the support base 100
is formed such that its both ends in the longitudinal direction are
inserted into the corresponding cutouts 112 respectively.
The respective two vibrators 102A, 102B and 102C, 102D, which are connected
to the both side surfaces of the support base 100, are provided with
plate-shaped driving sections (third plate-shaped sections) 114 which are
thin-walled in the direction of height and formed between the main
vibrator bodies 106 respectively. In the illustrative embodiment shown in
FIG. 22, each of the driving sections 114 has its upper surface which is
disposed on a side of the upper surface of the main vibrator body 106, and
which is disposed at a position nearest to the connecting sections 108.
The respective driving sections 114 are actually disposed on the side of
the upper surface of the main vibrator body 106. However, strictly
speaking, they are convex upward or convex downward, giving a structure in
which they are not in an identical plane (plate spring structure).
Plate-shaped sections 116, which are thin-walled in their direction of
height, are provided between portions of the both side surfaces of the
support base 100 in the vicinity of the both ends in the longitudinal
direction and side surfaces of the cutouts 112 opposing the portions. In
the illustrative embodiment shown in FIG. 22, the upper surfaces of the
respective plate-shaped sections 116 are depicted in a state in which they
are flush with the upper surface of the support base 100 and the upper
surface of the frame 104. However, in fact, although the respective
plate-shaped sections 116 are disposed on the side of the upper surface of
the support base 100 and on the side of the upper surface of the frame
104, they are convex upward or convex downward. Strictly speaking, the
respective plate-shaped sections 116 have a structure in which they are
not disposed in an identical plane (plate spring structure).
In the vibration gyro sensor according to the fifteenth embodiment, the
support base 100, the four vibrators 102A to 102D, the frame 104, the four
connecting sections 108, the two driving sections 114, and the four
plate-shaped sections 116 are constructed by an integrated fired product
made of ceramics. The vibration gyro sensor further comprises driving
piezoelectric/electrostrictive elements 118 formed on the driving sections
114, and detecting piezoelectric/electrostrictive elements 120 formed on
the plate-shaped sections 116. Accordingly, driving means 122 for
vibrating the vibrators 102 in an excited manner are constructed by the
driving sections 114 and the driving piezoelectric/electrostrictive
elements 118, and detecting sections 124 are constructed by the
plate-shaped sections 116 and the detecting piezoelectric/electrostrictive
elements 120. When the driving piezoelectric/electrostrictive elements 118
are operated by applying an electric power thereto, the respective two
vibrators 102A, 102B and 102C, 102D vibrate while being bent in mutually
opposite directions in the X axis direction, i.e., in directions to make
mutual approach or separation in the arrangement plane thereof.
The connecting sections 108 provided between the main vibrator bodies 106
and the support base 100 will now be described. The aspect ratio (width:
height) of the connecting section 108 is preferably within a range of
1:1.2 to 1:1000, and more preferably within a range of 1:1.8 to 1:50. The
aspect ratio should be designed within the foregoing range because when
the aspect ratio of the connecting section 108 is larger than 1:1.2,
unnecessary vibration in the Z axis direction tends to occur in the
vibrators 102A to 102D. As a result, unnecessary vibration tends to occur
in the detecting sections 124. On the other hand, if the aspect ratio is
smaller than 1:1000, it is difficult to process and machine the connecting
sections 108. As a result, the processing accuracy is deteriorated.
Since integrated firing of the ceramics and formation of the
piezoelectric/electrostrictive elements have been described in detail
above repetitive, explanation of those aspects of the present invention
will be omitted in this section.
In the vibration gyro sensor according to the fifteenth embodiment, when
the driving piezoelectric/electrostrictive elements 118 are operated, the
driving sections 114 undergo deformation. Thus the respective two
vibrators 102A, 102B and 102C, 102D vibrate laterally (lateral vibration)
(lateral vibration) in mutually opposite directions along the X axis.
When an angular velocity is applied around the axis (around the Z axis in
FIG. 22) perpendicular to the plane including the certain direction and
the extending direction of the support base 100 in a state in which the
respective two vibrators 102A, 102B and 102C, 102D are vibrated, a force
acts in the Y axis direction on the plate-shaped sections 116 of the
detecting sections 124. The force causes the detecting sections 124 to
make lateral vibration. Namely, rotational vibration occurs around the Z
axis, and the vibration is detected as an electromotive force (voltage) by
the piezoelectric/electrostrictive elements 120 of the detecting sections
124.
In the present invention, all of the vibrators 102, the support base 100,
and the detecting sections 124 are constructed by the integrated fired
product of ceramics. Therefore, there is no magnetic material such as the
conventional elinvar alloy in the materials for constructing the vibration
gyro sensor. Accordingly, the characteristics of the sensor are not
affected by any ambient magnetic field.
The detecting section 124 is constructed as having the plate-shaped section
116 which is more thin-walled than the main vibrator body 106 in its
direction of height so that it has a structure having low rigidity.
Therefore, when the vibration is caused around the Z axis by the angular
velocity as described above, a large strain or distortion is obtained in
the plate-shaped section 116. Thus it is possible to greatly improve the
detection sensitivity of the detecting piezoelectric/electrostrictive
element 120 formed on the plate-shaped section 116.
Especially, in the vibration gyro sensor according to the fifteenth
embodiment, the vibration is generated in the detecting section 124 only
when the angular velocity is applied. Therefore, the output (null
voltage), which is obtained from the detecting
piezoelectric/electrostrictive element 120 in a state in which no angular
velocity is applied, is extremely small. Thus the detection sensitivity is
greatly improved. Moreover, the probability of fatigue fracture at the
detecting section 124 due to vibration is lowered, and it is possible to
contemplate a long service life of the vibration gyro sensor.
The vibration gyro sensor has a structure not for measuring the angular
velocity around the major axis of the vibrator 106 (around the Y axis),
but instead for measuring the angular velocity around the axis
perpendicular to the plane which includes the certain direction and the
extending direction of the support base 100 (around the Z axis).
Therefore, the vibrators 102, the support base 100, and the frame 104 can
be made thin in their direction of height. Thus it is possible to
facilitate realization of a compact size and a light weight of the
vibration gyro sensor.
The four vibrators 102A to 102D have the structure in which each of the
main vibrator bodies 106 includes no thin-walled plate member and each of
them is supported singly by the support base 100 having the high strength.
Therefore, each of the main vibrator bodies 106 itself is allowed to have
a large mass. Accordingly, the Coriolis force (Fc=2 mv.OMEGA.) generated
in the vibrators 102A to 102D is increased, and hence it is possible to
realize a high sensitivity in relation to the detection of strain effected
by the detecting sections 124.
Next, a vibration gyro sensor according to a sixteenth embodiment will be
explained with reference to FIG. 23. Components or parts corresponding to
those shown in FIG. 22 are designated by the same reference numerals,
duplicate explanation of which will be omitted.
As shown in FIG. 23, the vibration gyro sensor according to the sixteenth
embodiment has approximately the same structure as that of the vibration
gyro sensor according to the fifteenth embodiment (see FIG. 22). However,
the detecting sections 124 are different in the following points.
Namely, the detecting section 124 comprises a ring member 130 formed of
ceramics in an integrated manner between a side surface of the cutout 112
and a portion of both side surfaces of the support base 100 in the
vicinity of the both ends in the longitudinal direction, a plate-shaped
section 116 provided in an integrated and bridged manner in parallel to
the extending direction of the support base 100 (X axis direction) in the
ring member 130, and a detecting piezoelectric/electrostrictive element
120 formed on the plate-shaped section 116.
The vibration gyro sensor according to the sixteenth embodiment is operated
as follows. Namely when an angular velocity is applied around the axis
perpendicular to the plane including the certain direction and the
extending direction of the support base 100 (around the Z axis) in a state
in which the respective two vibrators 102A, 102B and 102C, 102D are
vibrated in accordance with the operation of the driving
piezoelectric/electrostrictive elements 118, a force acts in the Y axis
direction on the detecting sections 124. The action of the force causes
the ring members 130 to make vibration while forming elliptic
configurations with their major or minor axis directed in the Y axis
direction. The vibration of the ring members 130 in the Y axis direction
is detected as an electromotive force (voltage) by the detecting
piezoelectric/electrostrictive elements 120. In the sixteenth embodiment,
the strain in the detecting sections 124 in the Y axis direction is
indirectly measured via the deformation of the ring members 130 by using
the detecting piezoelectric/electrostrictive elements 120. This embodiment
provides an effect that the vibration gyro sensor is excellent in
durability.
In the vibration gyro sensors according to the fifteenth and sixteenth
embodiments, the resonance frequency is adjusted in the same manner as,
for example, the vibration gyro sensor according to the first embodiment
described above (see FIG. 1). The adjustment for the resonance frequency
will be specifically explained with reference to FIGS. 24 and 25, as
represented by the vibration gyro sensor according to the fifteenth
embodiment.
The gyro sensor according to the fifteenth embodiment is actually
constructed as follows in order to adjust the resonance frequency. Namely,
as shown in FIG. 24, thin-walled first projections 132, which protrude
outwardly from respective free ends of the respective two vibrators 102A,
102B and 102C, 102D, are formed of ceramics in an integrated manner.
Further, thin-walled second projections 134, which protrude outwardly from
both ends of the support base 100 in the longitudinal direction, are
formed of ceramics in an integrated manner.
The resonance frequency for driving is adjusted by trimming-treating the
first projections 132, and the resonance frequency for detection is
adjusted by trimming-treating the second projections 134.
In this embodiment, the resonance frequency for driving can be adjusted by
applying a trimming treatment (excising treatment) to the first
projections 132, and the resonance frequency for detection can be adjusted
by applying a trimming treatment (excising treatment) to the second
projections 134. Namely, the resonance frequencies for driving and
detection can be independently adjusted, respectively. Therefore, for
example, it is possible to avoid the inconvenience that the resonance
frequency for detection is affected by adjustment for the resonance
frequency for driving.
The shapes of the first and second projections 132, 134 may by constructed
as follows. For example, as shown in FIG. 24, the first and second
projections 132, 134 may be constructed as plate-shaped and thin-walled in
the direction of height with respect to the respective main vibrator
bodies 106. Alternatively, as shown in FIG. 25, the first and second
projections 132, 134 may be constructed as plate-shaped and thin-walled in
the extending direction of the support base 100 (X axis direction) with
respect to the respective main vibrator bodies 106.
The shape shown in FIG. 24 is advantageous in that the trimming treatment
can be easily performed by means of, for example, laser beam scanning over
the upper surface. In the case of the shape shown in FIG. 25, regions to
be subjected to the trimming treatment are disposed over entire surfaces
perpendicular to the direction of vibration of the respective two
vibrators 102A, 102B and 102C, 102D, and hence an extremely excellent mass
balance is obtained. In this case, the trimming treatment is performed,
for example, by applying percussion such as ultrasonic waves after laser
radiation so that unnecessary portions are excised.
Actually, upon the adjustment for the resonance frequency, if the first
projections 132 are subjected to the trimming treatment in order to adjust
the resonance frequency for driving, the resonance frequency for detection
is considerably affected. However, even when the second projections 134
are subjected to the trimming treatment in order to adjust the resonance
frequency for detection, the resonance frequency for driving is not
affected. Therefore, when the resonance frequency is actually adjusted, it
is preferable that the resonance frequency for driving is firstly adjusted
by trimming-treating the first projections 132, and then the resonance
frequency for detection is adjusted by trimming-treating the second
projections 134.
Next, a vibration gyro sensor according to a seventeenth embodiment will be
explained with reference to FIG. 26. Components or parts corresponding to
those shown in FIG. 22 are designated by the same reference numerals,
duplicate explanation of which will be omitted.
As shown in FIG. 26, the vibration gyro sensor according to the seventeenth
embodiment is constructed in approximately the same manner as the
vibration gyro sensor according to the fifteenth embodiment. However, the
former is different from the latter in that plate-shaped driving sections
114 of the driving means 122 are arranged on lines for connecting centers
of gravity of the corresponding main vibrator bodies 106, respectively.
In this embodiment, the respective two vibrators 102A, 102B and 102C, 102D
can efficiently make mutual approach and separation, as compared with the
vibration gyro sensor including the driving sections 114 disposed in the
vicinity of the connecting sections 108 (for example, the vibration gyro
sensor according to the fifteenth embodiment). Accordingly, this
embodiment is advantageous in that the detection sensitivity in the
detecting sections 124 can be improved.
The adjustment for the resonance frequency by means of the trimming
treatment for the vibration gyro sensor may be performed in another way,
in place of the trimming treatment for the first and second projections
132, 134 described above (see FIGS. 24 and 25). As shown in FIG. 27, the
driving sections 114 provided between the respective main vibrator bodies
106, and the plate-shaped sections 116 of the detecting sections 124
provided between the support base 100 and the frame 104 are allowed to
have wide widths beforehand. The widths of the driving sections 114 and
the plate-shaped sections 116 are appropriately changed. Thus the
resonance frequencies for driving and detection may be adjusted.
In this adjustment method, the resonance frequencies for driving and
detection are not adjusted by changing the masses of the main vibrator
bodies 106 and the support base 100. Instead the resonance frequencies for
driving and detection are adjusted by changing spring constants of the
driving sections 114 and the plate-shaped sections 116.
Specifically, when the frequency for driving is changed, the two
plate-shaped driving sections 114 disposed between the respective main
vibrator bodies 106 are excised by means of, for example, laser machining
or ultrasonic machining. When the frequency for detection is changed, the
four plate-shaped sections 116 disposed between the support base 100 and
the frame 104 are excised by means of, for example, laser machining or
ultrasonic machining.
In this embodiment, it is unnecessary to form the first projections 132 and
the second projections 134 at the free ends of the respective main
vibrator bodies 106 and at the both ends of the support base 100 in the
longitudinal direction respectively. Accordingly, the production steps can
be simplified. Moreover, the resonance frequency is easily adjusted
because the region subjected to the trimming treatment is thin-walled.
Unlike the method in which the resonance frequency is adjusted by changing
the mass, the method of this embodiment is also advantageous in that the
resonance frequency for driving and the resonance frequency for detection
can be adjusted independently from each other.
The fifteenth to seventeenth embodiments are illustrative of the formation
of the driving section 114 between the main vibrator bodies 106. In
addition, the driving section 114 may be formed between the support base
100 and the main vibrator body 106. Several examples of this arrangement
are shown in FIGS. 28 and 29 as the eighteenth and nineteenth embodiments,
respectively.
Namely, as shown in FIG. 28, a vibration gyro sensor according to the
eighteenth embodiment comprises driving sections 114 each of which is
formed between a support base 100 and a portion of an end surface of a
main vibrator body 106 disposed on a side of the support base 100 in the
vicinity of a frame 104. As shown in FIG. 29, a vibration gyro sensor
according to the nineteenth embodiment comprises driving sections 114 each
of which is formed between a support base 100 and a portion corresponding
to a region of the end surface of the main vibrator body 106 on the side
of the support base 100 in the vicinity of the center of the support base
100 in the longitudinal direction.
In both of the vibration gyro sensors according to the eighteenth and
nineteenth embodiments, the driving section 114 is not formed between the
adjacent main vibrator bodies 106. Accordingly, it is possible to narrow
the spacing distance between the adjacent main vibrator bodies 106, making
it possible to facilitate realization of a compact size of the vibration
gyro sensor.
In the fifteenth to nineteenth embodiments, the connecting section 108,
which is formed between each of the main vibrator bodies 106 and the
support base 100, is disposed at the position on each of the main vibrator
bodies 106, the position being located at the central portion of the end
surface of the main vibrator body 106 on the side of the support base 100.
However, it is not necessarily indispensable that the position is the
central portion. For example, as shown in FIG. 30, the position, at which
the connecting section 108 is formed on each of the main vibrator bodies
106, may be disposed at a portion of the end surface of the main vibrator
body 106 on the side of the support base 100 in the vicinity of the frame
106 (twentieth embodiment). Although not shown, the position may be a
portion corresponding to a region of the end surface of the main vibrator
body 106 on the side of the support base 100 in the vicinity of the center
of the support base 100 in the longitudinal direction.
As shown in FIGS. 31 to 33, in order to maintain constant vibration of the
driving section 114 effected by the driving piezoelectric/electrostrictive
element 118 of the driving means 122, it is also preferable to adopt a
mechanism wherein a signal, which is obtained from a reference
piezoelectric/electrostrictive element 142 of a reference means 140
provided at a position different from that for the driving means 122, is
fed back to the driving means 122.
Namely, a vibration gyro sensor according to a twenty-first embodiment
shown in FIG. 31 is constructed such that the vibration gyro sensor
according to the seventeenth embodiment shown in FIG. 26 further comprises
reference means 140 provided in the vicinity of the connecting sections
108 of the respective main vibrator bodies 106. The reference means 140 is
constructed in approximately the same manner as the driving means 122,
comprising a plate-shaped reference section (fourth plate-shaped section)
144 which is thin-walled in the direction of height, and a reference
piezoelectric/electrostrictive element 142 formed on the reference section
144. The reference section 144 is formed of ceramics in an integrated
manner in the same manner as the driving section 114.
A signal, which is obtained from the reference
piezoelectric/electrostrictive element 142 of the reference means 140, is
fed to the driving piezoelectric/electrostrictive element 118 in the
feedback manner to give constant vibration of the driving means 122 formed
on the line for connecting the centers of gravity of the respective main
vibrator bodies 106.
In the embodiment described above, the plate-shaped section provided on the
line for connecting the centers of gravity of the respective main vibrator
bodies 106 and the piezoelectric/electrostrictive element formed on the
plate-shaped section are used as the driving means 122, and the
plate-shaped section provided in the vicinity of the connecting section
108 of each of the main vibrator bodies 106 and the
piezoelectric/electrostrictive element formed on the plate-shaped section
are used as the reference means 140. However, an arrangement in which the
driving means 122 and the reference means 140 are disposed in an inverse
manner is also allowed.
Next, a vibration gyro sensor according to a twenty-second embodiment shown
in FIG. 32 is constructed such that the vibration gyro sensor according to
the eighteenth embodiment shown in FIG. 28 further comprises reference
means 140 provided between the support base 100 and a portion
corresponding to a region of the end surface of the main vibrator body 106
on the side of the support base 100 in the vicinity of the center of the
support base 100 in the longitudinal direction.
A signal, which is obtained from a reference piezoelectric/electrostrictive
element 142 of the reference means 140, is fed back to the driving
piezoelectric/electrostrictive element 118 to give constant vibration of
the driving means 122 provided between the support base 100 and a portion
of the end surface of the main vibrator body 106 on the side of the
support base 100 in the vicinity of the frame 104.
In the embodiment described above, the plate-shaped section provided
between the support-base 100 and the portion of the end surface of the
main vibrator body 106 on the side of the support base 100 in the vicinity
of the frame 104 and the piezoelectric/electrostrictive element formed on
the plate-shaped section are used as the driving means 122. By contrast
the plate-shaped section provided between the support base 100 and the
portion corresponding to the region of the end surface of the main
vibrator body 106 on the side of the support base 100 in the vicinity of
the center of the support base 100 in the longitudinal direction and the
piezoelectric/electrostrictive element formed on the plate-shaped section
are used as the reference means 140. However, an arrangement in which the
driving means 122 and the reference means 140 are disposed in an inverse
manner may be utilized.
Next, a vibration gyro sensor according to a twenty-third embodiment shown
in FIG. 33 is constructed such that the vibration gyro sensor according to
the seventeenth embodiment shown in FIG. 26 further comprises a reference
means 140 provided between the support base 100 and a portion
corresponding to a region of the end surface of the main vibrator body 106
on the side of the support base 100 in the vicinity of the center of the
support base 100 in the longitudinal direction.
A signal, which is obtained from a reference piezoelectric/electrostrictive
element 142 of the reference means 140, is fed back to the driving
piezoelectric/electrostrictive element 118 to give constant vibration of
the driving means 122 formed on the line for connecting the centers of
gravity of the respective main vibrator bodies 106.
In the embodiment described above, the plate-shaped section provided on the
line for connecting the centers of gravity of the respective main vibrator
bodies 106 and the piezoelectric/electrostrictive element formed on the
plate-shaped section are used as the driving means 122, and the
plate-shaped section provided between the support base 100 and the portion
corresponding to the region of the end surface of the main vibrator body
106 on the side of the support base 100 in the vicinity of the center of
the support base 100 in the longitudinal direction and the
piezoelectric/electrostrictive element formed on the plate-shaped section
are used as the reference means 140. However, it is allowable to adopt an
arrangement in which the driving means 122 and the reference means 140 are
disposed in an inverse manner.
Any of the vibration gyro sensors according to the first to twenty-third
embodiments has the structure of the so-called forced vibration system in
which the vibrator 2 (or 102) is directly vibrated by the driving section.
However, as shown in FIGS. 34 to 36, it is allowable to adopt structures
based on the free vibration system.
At first, a vibration gyro sensor according to a twenty-fourth embodiment
shown in FIG. 34 will be described. This vibration gyro sensor is
illustrative of a structure comprising plate-shaped vibration-applying
sections (fifth plate-shaped sections) 150 arranged between a support base
100 and respective main vibrator bodies 106 and extending in parallel to
the longitudinal direction of the support base 100, thin-walled
plate-shaped first connecting sections (sixth plate-shaped sections) 152
for connecting the support base 100 and the vibration-applying sections
150, thin-walled plate-shaped connecting sections (seventh plate-shaped
sections) 154 for connecting the main vibrator bodies 106 and the
vibration-applying sections 150, and driving means 122 provided between
the respective vibration-applying sections 150.
The first and second connecting sections 152, 154 have approximately the
same dimensional relation as those of the connecting sections 108 of the
vibration gyro sensors according to the fifteenth to twenty-third
embodiments described above. The height of the vibration-applying section
150 is approximately the same as that of the main vibrator body 106. The
width of the vibration-applying section 150 is designed to be smaller than
the width of the main vibrator body 106 and slightly larger than those of
the first and second connecting sections 152, 154.
A vibration gyro sensor according to a twenty-fifth embodiment shown in
FIG. 35 is constructed in approximately the same manner as the vibration
gyro sensor according to the twenty-fourth embodiment. However, the former
is different from the latter in that the driving means 122 is provided
between the support base 10 and a portion of the end surface of the
vibration-applying section 150 on the side of the support base 100 in the
vicinity of the frame 104.
A vibration gyro sensor according to a twenty-sixth embodiment shown in
FIG. 36 is constructed in approximately the same manner as the vibration
gyro sensor according to the twenty-fourth embodiment. However, the former
is different from the latter in that the driving means 122 is provided
between the support base 10 and a portion corresponding to a region of the
end surface of the vibration-applying section 150 on the side of the
support base 100 in the vicinity of the center of the support base 100 in
the longitudinal direction.
In the vibration gyro sensors according to the twenty-fourth to
twenty-sixth embodiments, the vibrators 102A to 102D are indirectly
vibrated by giving vibration to the vibration-applying sections 150
disposed between the main vibrator bodies 106 and the support base 100 by
the aid of the driving means 122. These vibration gyro sensors are
advantageous in the following points because the main vibrator bodies 106
are scarcely affected by the driving sections 114. Namely, (1) it is easy
to obtain large amplitude when the vibrators 102A to 102D are vibrated,
and (2) the vibration waveform rarely suffers disturbance in the vibrators
102A to 102D, and it is possible to obtain a vibration waveform following
the regular sine wave.
Vibration gyro sensors, which have been hitherto used, employ the elinvar
alloy for the vibrator in many cases, in which the bulky
piezoelectric/electrostrictive element formed with the electrodes is fixed
to the vibrator by means of adhesion. Therefore, it is necessary to use,
for example, solder or Ag paste for connecting external wiring to the
electrodes of the piezoelectric/electrostrictive element. In this
procedure, for example, the solder, the Ag paste, and the external wiring
itself behave as added weights which greatly affect the vibration
characteristics of the vibrator, making it difficult to produce the
vibration gyro sensors.
A vibration gyro sensor of another type is also known, in which a
piezoelectric ceramic is used for the vibrator. However, such vibration
gyro sensors are not essentially different from the foregoing conventional
vibration gyro sensors in that the lead wire is connected to the part
which is used to make vibration. Problems arise in that (a) the connecting
section to the external wiring is less reliable, and (b) the dispersion in
production is large.
On the contrary, the vibration gyro sensors according to the first to
twenty-sixth embodiments described above are advantageous in that external
wiring can be easily connected to the pair of electrodes of the respective
piezoelectric/electrostrictive elements 118, 120.
This advantage will be explained on the basis of the vibration gyro sensor
according to the seventeenth embodiment shown in FIG. 26. As shown in FIG.
37, the vibration gyro sensor is constructed by the integrated fired
product made of ceramics (non-conductive materials) except for the
respective pairs of electrodes of the driving means 122 and the detecting
sections 124. Accordingly, the pair of electrodes for constructing the
piezoelectric/electrostrictive element 118 of the driving means 122, two
external wirings (160, 162) and (164, 166) led from the pair of
electrodes, the pair of electrodes for constructing the
piezoelectric/electrostrictive element 120 of the detecting section 124,
and two external wirings (168, 170), (172, 174), (176, 178) and (180, 182)
led from the pair of electrodes can be formed with an identical wiring
material in accordance with the film formation method respectively.
The wiring formation pattern will be specifically explained below. The two
wirings (160, 162) and (164, 166) which are led from the pairs of
electrodes for constructing the piezoelectric/electrostrictive elements
118 of the driving means 122 provided between the respective main vibrator
bodies 106, are formed such that they are led to the frame 104 via the
upper surfaces of the main vibrator bodies 106 adjacent to the respective
electrodes, the upper surfaces of the connecting sections 108, the upper
surface of the support base 100, and the upper surfaces of the
plate-shaped sections 116 of the detecting sections 124 adjacent to the
vibrators 102A, 102B.
The two wirings (168, 170), (172, 174), (176, 178) and (180, 182) which are
led from the pairs of electrodes of the piezoelectric/electrostrictive
elements 120 of the respective detecting sections 124 are formed such that
they are led to the frame 104 from the respective detecting sections 124.
As described above, the material for constructing the electrodes and the
wirings is not specifically limited provided that the material is a
conductor which can withstand the oxidizable atmosphere at a high
temperature of a degree of the heat treatment temperature and the firing
temperature. For example, the material may be a simple substance of metal
or an alloy. The material may be a mixture of a metal or an alloy and an
additive such as an insulative ceramic and glass. Further, no problem
occurs when the material is a conductive ceramic. More appropriately, it
is preferable to use electrode materials comprising major components of
high melting point noble metals such as platinum, palladium, and rhodium,
and alloys such as silver-palladium, silver-platinum, and
platinum-palladium.
As for the method for forming the electrodes and the wirings, it is
possible to appropriately adopt, for example, thick film methods such as
screen printing, application methods such as dipping, and thin film
methods such as ion beam, sputtering, vacuum vapor deposition, ion
plating, CVD, and plating. However, there is no limitation thereto.
Next, other embodiments will be further explained. The embodiments
described below may be grasped as modified embodiments of the various
embodiments shown in FIGS. 1 to 21. Accordingly, components or parts
corresponding to those shown in FIGS. 1 to 21 are designated by the same
reference numerals, and duplicate explanation will be omitted.
At first, a vibration gyro sensor according to a twenty-seventh embodiment
shown in FIG. 38 is constructed in approximately the same manner as the
vibration gyro sensor according to the first embodiment shown in FIG. 1.
However, the former is different from the latter in that a third
plate-shaped section 10, on which a driving piezoelectric/electrostrictive
element 14 is provided, is formed in an integrated manner so that the two
second plate-shaped sections 8 are bridged with the third plate-shaped
section 10.
A vibration gyro sensor according to a twenty-eighth embodiment shown in
FIG. 39 is constructed in approximately the same manner as the vibration
gyro sensor according to the third embodiment shown in FIG. 5. However,
the former is different from the latter in that thin-walled third
plate-shaped sections 10 are formed in an integrated manner between the
support bar 28 and the second plate-shaped sections 8 disposed at the
right and left thereof, and driving piezoelectric/electrostrictive
elements 14 are formed on the third plate-shaped sections 10,
respectively, so that the right and left two vibrators 2 are vibrated in
an excited manner in mutually opposite directions by operating the driving
piezoelectric/electrostrictive elements 14, respectively.
A vibration gyro sensor according to a twenty-ninth embodiment shown in
FIG. 40 is constructed in approximately the same manner as the vibration
gyro sensor according to the fifth embodiment shown in FIG. 7. However,
the former is different from the latter in that thin-walled third
plate-shaped sections 10 are formed in an integrated manner between the
two second plate-shaped sections 8 and sides of the attachment frame 30
opposing thereto. Moreover, the driving piezoelectric/electrostrictive
elements 14 are formed in an integrated manner on the third plate-shaped
sections 10 in accordance with the film formation method.
A vibration gyro sensor according to a thirtieth embodiment shown in FIG.
41 is constructed in approximately the same manner as the vibration gyro
sensor according to the seventh embodiment shown in FIG. 9. However, the
former is different from the latter in that a thin-walled third
plate-shaped section 10 is formed in an integrated manner between the two
second plate-shaped sections 8 disposed in the attachment frame 30 having
the rectangular frame structure. In addition, a driving
piezoelectric/electrostrictive element 14 is formed in an integrated
manner on the third plate-shaped section 10 in accordance with the film
formation method.
The vibration gyro sensors according to the twenty-seventh to thirtieth
embodiments are constructed such that the vibrators 2 are not driven
directly, but the second plate-shaped sections 8 are driven. Accordingly,
the vibrators 2 can make vibration without being restricted by the third
plate-shaped section 10 which constructs the driving means 122. Therefore,
the Q factor of the vibrator 2 is increased, and hence the vibration is
not readily attenuated. Thus it is easy to handle the detection signal
detected by the detecting piezoelectric/electrostrictive element 12.
Further, the amplitude of vibration of the vibrator 2 is increased, and it
is possible to further improve the sensitivity.
In the vibration gyro sensors according to the first to thirtieth
embodiments, the first plate-shaped section 6 for constructing the
detecting section is formed to be more thin-walled than the vibrator 2,
and they are integrated with each other in structure. However, in view of
the function, the first plate-shaped section 6 or the detecting section is
constructed distinctly from the vibrator 2.
The following various embodiments are constructed such that the vibrator 2
and the detecting section are integrated with each other both in structure
and function. Such embodiments are more advantageous in order to improve
the sensitivity. Explanation for such embodiments will be made in an
specified manner below. Components or parts corresponding to those shown
in FIGS. 1 to 21 are designated by the same reference numerals, duplicate
explanation of which will be omitted.
At first, a vibration gyro sensor according to a thirty-first embodiment
shown in FIG. 42 is constructed in an integrated manner by using an
integrated fired product made of ceramics to have a structure comprising a
rectangular block-shaped support base 4 having a predetermined thickness,
two second plate-shaped sections 8 which extend from proximal ends on a
longitudinal side surface of the support base 4 in a direction
perpendicular to the longitudinal side surface of the support base 4 while
being separated from each other by a predetermined spacing distance, two
first plate-shaped sections 6 each having an approximately strip-shaped
(wide and lengthy) planar configuration which extend from proximal ends on
upper portions of free ends of the respective second plate-shaped sections
8 in the direction perpendicular to the longitudinal side surface of the
support base 4 while being separated from each other by a predetermined
spacing distance (see FIG. 43), and a third plate-shaped section 10 having
an approximately strip-shaped planar configuration formed to bridge the
two second plate-shaped sections 8 therewith. In this embodiments,
vibrators 2 are constructed by the first plate-shaped sections 6.
The width of the second plate-shaped section 8 is thinner than the width of
the first plate-shaped section 6. The second plate-shaped section 8 is a
thin-walled plate-shaped section having a principal surface which extends
in the direction perpendicular to the first plate-shaped section 6. The
first plate-shaped section 6 (vibrator 2) is connected in an integrated
manner to the support base 4 via the second plate-shaped section 8.
The third plate-shaped section 10 is connected in an integrated manner
between portions of the second plate-shaped sections 8 in the vicinity of
the support base 4.
In the vibration gyro sensor according to the thirty-first embodiment,
detecting piezoelectric/electrostrictive elements 12 are formed on
approximately entire surfaces of upper surfaces of the respective first
plate-shaped sections 6 which are formed to be wide. A driving
piezoelectric/electrostrictive element 14 is formed on an approximately
entire surface of an upper surface of the third plate-shaped section 10.
In the vibration gyro sensor according to the thirty-first embodiment, the
vibrator 2 is constructed by the wide and lengthy first plate-shaped
section 6. Accordingly, the vibrator 2 has a large mass and a large
moment. As a result, the velocity (a amplitude) brought about by the
driving vibration is increased. Therefore, it is possible to further
improve the sensitivity. Further, the detecting
piezoelectric/electrostrictive element 12 is formed on the approximately
entire surface of the first plate-shaped section 6. Therefore, it is
possible to accumulate a large amount of electric charge, and thus this
embodiment is advantageous in the current detection system.
A vibration gyro sensor according to a thirty-second embodiment shown in
FIG. 44 is constructed in approximately the same manner as the vibration
gyro sensor according to the thirty-first embodiment (see FIG. 42).
However, the former is different from the latter in that thick-walled
block sections 70 are formed in an integrated manner between the first
plate-shaped sections 6 and the second plate-shaped sections 8
respectively.
In the vibration gyro sensor according to the thirty-first embodiment shown
in FIG. 42, the first plate-shaped section 6 is directly formed on the
second plate-shaped section 8. Therefore, it is feared that the boundary
portion between the first plate-shaped section 6 and the second
plate-shaped section 8 may be disadvantageous from a viewpoint of
strength. However, in the vibration gyro sensor according to the
thirty-second embodiment, the presence of the block section 70 makes it
possible to increase the strength of the boundary portion. Accordingly,
this embodiment is advantageous to improve the reliability.
Next, a vibration gyro sensor according to a thirty-third embodiment shown
in FIG. 45 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-first embodiment shown in
FIG. 42. However, the former is different from the latter in that the
support base 4 is provided as a rectangular frame 32. Two second
plate-shaped sections 8 are formed in an integrated manner so that they
extend from proximal ends disposed on one short side of inner frame wall
surfaces of the frame 32 in a direction parallel to long sides of the
frame 32 while being separated from each other by a predetermined spacing
distance.
For example, the vibration gyro sensor according to the thirty-first
embodiment shown in FIG. 42 includes the block-shaped support base 4.
Therefore, such a vibration gyro sensor suffers a from installation
problem in that when the support base 4 is installed and fixed by using an
adhesive or the like, the area for fixation is small. It also suffers from
strength problems since the rigidity of the support base 4 tends to be
lowered, and the vibration is transmitted to the support bars 4. However,
in this embodiment, the support base 4 is provided in the form of the
frame 32, and thus the degree of freedom for attachment is increased.
Further, the rigidity is also improved. Therefore, the foregoing problems
can be solved, and hence this embodiment is practically appropriate.
Next, a vibration gyro sensor according to a thirty-fourth embodiment shown
in FIG. 46 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-third embodiment (FIG. 45).
However, the former is different from the latter in that thick-walled
block sections 70 are formed in an integrated manner between the first
plate-shaped sections 6 and the second plate-shaped sections 8,
respectively.
In this embodiment, the presence of the block section 70 makes it possible
to increase the strength of the boundary portion between the first
plate-shaped section 6 and the second plate-shaped section 8. Further,
this embodiment is advantageous from viewpoints of installation and
rigidity because the frame 32 is used.
Next, a vibration gyro sensor according to a thirty-fifth embodiment shown
in FIG. 47 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-third embodiment (FIG. 45).
However, the former is different from the latter in that a plurality of
recesses 72 are formed on the back surface of the first plate-shaped
section 6 as shown in FIG. 48. Moreover detecting
piezoelectric/electrostrictive elements 12 are formed in an array of
islands at positions on the upper surface of the first plate-shaped
section 6 corresponding to the plurality of recesses 72. The embodiment
shown in FIG. 47 is illustrative of a structure in which the recess 72 has
a circular contour, and the detecting piezoelectric/electrostrictive
element 12 has a circular planar configuration.
In the vibration gyro sensor according to the thirty-third embodiment, the
strength is lowered at the portions of the first plate-shaped section 6 on
which the recesses 72 are formed. Therefore, when the first plate-shaped
section 6 is deformed by the Coriolis force, a strain, which is larger
than that obtained at portions without having any recess 72, is generated
at the portions on which the recesses 72 are formed. Accordingly, a large
detection output can be obtained by forming the detecting
piezoelectric/electrostrictive elements 12 at the portions corresponding
to the recesses 72. Thus it is possible to further improve the
sensitivity.
Next, a vibration gyro sensor according to a thirty-sixth embodiment shown
in FIG. 49 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-fifth embodiment shown in
FIG. 47. However, the former is different from the latter in that
thick-walled block sections 70 are provided in an integrated manner
between the first plate-shaped sections 6 and the second plate-shaped
sections 8, respectively.
In this embodiment, the presence of the block section 70 makes it possible
to increase the strength of the boundary portion between the first
plate-shaped section 6 and the second plate-shaped section 8. Further,
this embodiment is advantageous in terms of reliability and sensitivity,
because a large output can be obtained.
The vibration gyro sensors according to the thirty-fifth and thirty-sixth
embodiments described above are illustrative of the structure in which the
detecting piezoelectric/electrostrictive elements 12 each having the
approximately circular planar configuration are formed in the array of
islands on the upper surface of the first plate-shaped section 6.
Alternatively, as shown in FIGS. 50 and 51, both of the contour of each of
the recesses 72 (see FIG. 48) and the detecting
piezoelectric/electrostrictive elements 12 may be square or rectangular
(thirty-seventh and thirty-eighth embodiments). Those conceivable as the
planar configuration of the recess 72 and the detecting
piezoelectric/electrostrictive element 12 include, for example, circular
and rectangular configurations as described above, as well as rhombic
configurations. The shape of these components is not specifically limited.
Next, a vibration gyro sensor according to a thirty-ninth embodiment shown
in FIG. 52 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-first embodiment shown in
FIG. 42. However, the former is different from the latter in that an
attachment section 74 for fixing the support base 4 is provided in an
integrated manner on a surface of the support base 4 opposite to the
surface on which the second plate-shaped sections 8 are formed. In
addition, a support section (fifth plate-shaped section) 76, which is
thin-walled in the widthwise direction of the support base 4, is provided
in an integrated manner between the support base 4 and the attachment
section 74.
Namely, the vibration gyro sensor according to the thirty-ninth embodiment
has a structure in which a tuning fork 78 is constructed by the support
base 4, the two second plate-shaped sections 8, and the two vibrators 2
(first plate-shaped sections 6), and the tuning fork 78 is connected in an
integrated manner to the attachment section 74 via the support section
(fifth plate-shaped section) 76.
In general, the mode, which is obtained when the tuning fork 78 is
supported by an arbitrary fixing means with a support rod and the tuning
fork 78 is vibrated, includes a mode in which the two vibrators 2 of the
tuning fork 78 are vibrated in mutually opposite directions, and a mode in
which the two vibrators 2 are vibrated in an identical direction,
respectively.
The mode, which is required for the vibration gyro sensor, is the former
mode (the mode of vibration in mutually opposite directions). The latter
mode is an unnecessary mode for the vibration gyro sensor. Accordingly,
when the frequency of the necessary mode is greatly different from the
frequency of the unnecessary mode, they can be easily discriminated from
each other, and the detection accuracy in the necessary mode can be
improved.
FIG. 53 shows how the frequency in the necessary mode and the frequency in
the unnecessary mode change depending on the length of the support rod. In
FIG. 53, a curve "a" indicates a characteristic of the necessary mode, and
a curve "b" indicates a characteristic of the unnecessary mode. As
understood from FIG. 53, when the length of the support rod is large, the
frequencies in the both modes greatly differ. However, as the support rod
becomes short, the frequencies in the both modes approach to one another,
and it is difficult to discriminate them from each other. Therefore, the
short length is disadvantageous from a viewpoint of detection accuracy.
On the contrary, in the vibration gyro sensor according to the thirty-ninth
embodiment, the support base 4 is connected in the integrated manner to
the attachment section 74 via the support section 76. Therefore, the
support section 76 functions as the support rod, making it possible to
improve the detection accuracy.
Next, a vibration gyro sensor according to a fortieth embodiment shown in
FIG. 54 is constructed in approximately the same manner as the vibration
gyro sensor according to the thirty-ninth embodiment shown in FIG. 52.
However, the former is different from the latter in that thick-walled
block sections 70 are provided in an integrated manner between the first
plate-shaped sections 6 and the second plate-shaped sections 8
respectively.
In this embodiment, the presence of the block section 70 makes it possible
to increase the strength of the boundary portion between the first
plate-shaped section 6 and the second plate-shaped section 8. Moreover,
the vibration gyro sensor has a tuning fork 78 which is constructed in an
integrated manner on the support section 76. Therefore, this embodiment is
advantageous in order to improve the detection accuracy.
Next, a vibration gyro sensor according to a forty-first embodiment shown
in FIG. 55 is constructed in approximately the same manner as the
vibration gyro sensor according to the thirty-ninth embodiment shown in
FIG. 52. However, the former is different from the latter in that the
attachment section 76 has a form of a rectangular frame (hereinafter
referred to as "attachment frame 80"). The support section 76 is formed in
an integrated manner so that it extends from its proximal end disposed on
one short side of inner frame wall surfaces of the attachment frame 80 in
a direction parallel to long sides of the attachment frame 80.
In this embodiment, it is possible to improve the detection accuracy. This
embodiment is practically preferred from viewpoints of, for example, the
degree of freedom for attachment and rigidity, because the attachment
section is provided in the form of the attachment frame 80.
Next, a vibration gyro sensor according to a forty-second embodiment shown
in FIG. 56 is constructed in approximately the same manner as the
vibration gyro sensor according to the forty-first embodiment shown in
FIG. 55. However, the former is different from the latter in that
thick-walled block sections 70 are provided in an integrated manner
between the first plate-shaped sections 6 and the second plate-shaped
sections 8, respectively.
In this embodiment, the presence of the block section 70 makes it possible
to increase the strength of the boundary portion between the first
plate-shaped section 6 and the second plate-shaped section 8. Moreover,
this embodiment is advantageous from viewpoints of installation and
rigidity, because the attachment frame 80 is used.
Next, a vibration gyro sensor according to a forty-third embodiment shown
in FIG. 57 is constructed in approximately the same manner as the
vibration gyro sensor according to the forty-first embodiment shown in
FIG. 55. However, the former is different from the latter in that a
plurality of recesses 72 are formed on the back surface of the first
plate-shaped section 6 as shown in FIG. 48, and detecting
piezoelectric/electrostrictive elements 12 are formed in an array of
islands at positions on the upper surface of the first plate-shaped
section 6 corresponding to the plurality of recesses 72. The embodiment
shown in FIG. 57 is illustrative of a structure in which the recess 72 has
a circular contour, and the detecting piezoelectric/electrostrictive
element 12 has a circular planar configuration.
In this embodiment, it is possible to improve the detection accuracy, and a
large detection output can be obtained. Thus, it is possible to improve
the sensitivity.
Next, a vibration gyro sensor according to a forty-fourth embodiment shown
in FIG. 58 is constructed in approximately the same manner as the
vibration gyro sensor according to the forty-third embodiment shown in
FIG. 57. However, the former is different from the latter in that
thick-walled block sections 70 are provided in an integrated manner
between the first plate-shaped sections 6 and the second plate-shaped
sections 8, respectively.
In this embodiment, the presence of the block section 70 makes it possible
to increase the strength of the boundary portion between the first
plate-shaped section 6 and the second plate-shaped section 8. Moreover, a
large output can be obtained. Accordingly, this embodiment is advantageous
in view of high reliability and improvement in sensitivity.
The vibration gyro sensors according to the forty-third and forty-fourth
embodiments described above are illustrative of the structure in which the
detecting piezoelectric/electrostrictive elements 12 each having the
approximately circular planar configuration are formed in the array of
islands on the upper surface of the first plate-shaped section 6.
Alternatively, as shown in FIGS. 59 and 60, both of the contour of each of
the recesses 72 (see FIG. 48) and the detecting
piezoelectric/electrostrictive elements 12 may be square or rectangular
(forty-fifth and forty-sixth embodiments). In these embodiments, those
conceivable as the planar configuration of the recess 72 and the detecting
piezoelectric/electrostrictive element 72 also include, for example,
circular and rectangular configurations as described above, as well as
rhombic configurations. The shape of these components is not specifically
limited.
In the vibration gyro sensors according to the thirty-first through
forty-sixth embodiments, the driving means 122, which has the driving
section (third plate-shaped section) 10 with the driving
piezoelectric/electrostrictive element 14 formed on its upper surface, is
provided in the integrated manner between the second plate-shaped sections
8. Alternatively, as shown in FIG. 61, it is preferable to adopt a
mechanism wherein a signal, which is obtained from a reference means 140
disposed at a position different from that of the driving section 10, is
fed back to the driving means 122 in order to maintain constant vibration
of the vibrators 2.
Namely, a vibration gyro sensor according to a forty-seventh embodiment
shown in FIG. 61 has such a structure that the vibration gyro sensor
according to the thirty-fourth embodiment (see FIG. 46) further comprises
the reference means 140 which is provided in parallel to the driving means
122 between the two second plate-shaped sections 8.
The reference means 140 is constructed in approximately the same manner as
the driving means 122, comprising a plate-shaped reference section (fourth
plate-shaped section) 144 which is thin-walled in its direction of height,
and a reference piezoelectric/electrostrictive element 142 formed on the
reference section 144. The reference section 144 is integrally formed of
ceramics in the same manner as the driving section 10. The reference
section 144 and the driving section 10 are arranged in accordance with the
following relation. Namely, the driving section 10 is formed in an
integrated manner at a position close to the frame 80 between the second
plate-shaped sections 8. The reference section 144 is formed in an
integrated manner at a position slightly nearer to the first plate-shaped
sections 6 as compared with the driving section 10.
The signal, which is obtained from the reference
piezoelectric/electrostrictive element 142 of the reference means 140, is
fed back to the driving piezoelectric/electrostrictive element 14 in order
to give constant vibration of the driving means 122 formed between the
second plate-shaped sections 8.
As shown in FIG. 62, the driving signal is supplied to the driving means
122 via lead wires 200a, 200b connected to upper and lower electrodes (not
shown) formed on upper and lower surfaces of the driving
piezoelectric/electrostrictive element 14. The reference signal is
obtained from the reference means 140 via lead wires 202a, 202b connected
to upper and lower electrodes (not shown) formed on upper and lower
surfaces of the reference piezoelectric/electrostrictive element 142.
The detection signal is obtained from the detecting
piezoelectric/electrostrictive element 12 formed on the first plate-shaped
section 6 via lead wires 204a, 204b connected to upper and lower
electrodes (not shown) formed on upper and lower surfaces of the detecting
piezoelectric/electrostrictive element 12.
Other embodiments, in which the reference means 140 is formed, will be
explained below. At first, a vibration gyro sensor according to a
forty-eighth embodiment shown in FIG. 63 has such a structure that the
vibration gyro sensor according to the thirty-sixth embodiment shown in
FIG. 49 further comprises a reference means 140 which is provided in
parallel to the driving means 122 between the two second plate-shaped
sections 8.
This embodiment is constructed as shown in FIG. 64. Namely, the respective
upper electrodes of the plurality of detecting
piezoelectric/electrostrictive elements 12 formed in the array of islands
are electrically connected to lead wires 204a via mediating conductors
206a, respectively. The respective lower electrodes of the plurality of
detecting piezoelectric/electrostrictive elements 12 are electrically
connected to lead wires 204b via mediating conductors 206b, respectively.
The detection signal is obtained from the detecting
piezoelectric/electrostrictive elements 12 via the lead wires 204a, 204b.
Next, a vibration gyro sensor according to a forty-ninth embodiment shown
in FIG. 65 is constructed as follows, based on the vibration gyro sensor
according to the thirty-ninth embodiment (see FIG. 52). Namely, a
mediating section (sixth plate-shaped section) 208 having a free end is
provided in an integrated manner at an approximately central portion of a
side surface of the support base 4 facing the vibrators 2. A driving means
122 is provided in an integrated manner between the mediating section 208
and one of the second plate-shaped sections 8. A reference means 140 as
described above is provided in an integrated manner between the mediating
section 208 and the other second plate-shaped section 8.
This embodiment is based on the use of the following feature. Namely, the
support section 76 (fifth plate-shaped section) is formed between the
support base 4 and the attachment section 74 so that the support section
76 is disposed at a position which is approximately coincides with the
position of the line symmetry of the tuning fork 78. Accordingly, when one
of the two second plate-shaped sections 8 is vibrated to vibrate the
corresponding vibrator 2, the other vibrator 2 is vibrated at an identical
frequency.
Therefore, when one of the vibrators 2 is vibrated by operating the driving
means 122, the other vibrator 2 is also vibrated at an identical
frequency. Therefore, a signal obtained by the reference means 140 may be
used to perform feedback control so that the vibration of the driving
means 122 remains constant.
Next, a vibration gyro sensor according to a fiftieth embodiment shown in
FIG. 66 is constructed as follows, based on the vibration gyro sensor
according to the thirty-ninth embodiment (see FIG. 52). Namely, a
plurality of mediating sections 210a, 210b having respective free ends are
provided in an integrated manner at positions of both ends in the
longitudinal direction on a side surface of the support base 4 facing to
the vibrators 2. A driving means 122 is provided in an integrated manner
between one of the second plate-shaped sections 8 and one of the mediating
sections 210a. A reference means 140 is provided in an integrated manner
between the other second plate-shaped section 8 and the other mediating
section 210b.
In this embodiment, when one of the vibrators 2 is vibrated by operating
the driving means 122, the other vibrator 2 is also vibrated at an
identical frequency in the same manner described above. Therefore, a
signal obtained by the reference means 140 may be used to perform feedback
control so that the vibration of the driving means 122 is constant.
The vibration gyro sensors according to the forty-ninth and fiftieth
embodiments have the structure in which the tuning fork 78 is provided in
the integrated manner on the block-shaped attachment section 74.
Alternatively, the attachment section 74 is provided as a rectangular
frame (attachment frame) 80, as exemplified by vibration gyro sensors
according to fifty-first and fifty-second embodiments shown in FIGS. 67
and 68.
In these embodiments, the reference means 140 may be used to perform
feedback control so that the vibration effected by the driving means 122
is constant. Further, these embodiments are advantageous from viewpoints
of, for example, the degree of freedom for attachment and rigidity,
because the attachment section is provided as the attachment frame 80.
Next, a vibration gyro sensor according to a fifty-third embodiment shown
in FIG. 69 is constructed in approximately the same manner as the
vibration gyro sensor according to the forty-second embodiment shown in
FIG. 56. However, the former is different from the latter in that the
support section 76 is constructed as follows.
Namely, the support section 76 comprises a first support section 212
provided in an integrated and bridged manner to bridge a pair of inner
wall surfaces of inner wall surfaces of the attachment frame 80 along the
extending direction of the vibrators 2 so that the vibrators 2 are
disposed thereover as shown in FIGS. 70A and 70C, and a second support
section 214 provided in an integrated and bridged manner to bridge the
first support section 212 and the support base 4 so that the driving means
122 is disposed thereover as shown in FIG. 70B.
As described above, when the support rod for the tuning fork 78 is
elongated, it is possible to more clearly discriminate the necessary mode
from the unnecessary mode. Accordingly, the elongation of the support rod
for the tuning fork 78 is preferred in order to improve the detection
accuracy of the sensor. However, the vibration gyro sensor according to
the forty-second embodiment (see FIG. 56) has the structure in which the
support section 76 constructed by the fifth plate-shaped section is
provided in the integrated manner between the support base 4 and the
attachment frame 80. Therefore, if the support section 76 is elongated,
the entire length of the sensor is also elongated in accordance therewith.
Accordingly, the elongation of the support section 76 is limited.
On the contrary, in the vibration gyro sensor according to the fifty-third
embodiment, the second support section 214, which functions in
substantially the same manner as the support rod for the tuning fork 78,
is provided in parallel to the two second plate-shaped sections 8, giving
the structure in which the second support section 214 extends in the same
direction as the second plate-shaped sections 8. Therefore, even when the
length of the second support section 214 is elongated, the entire length
of the sensor is not changed until the length of the second support
section 214 exceeds a certain range. Accordingly, the second support
section 214 can be elongated, and it is possible to realize further
improvement in detection accuracy.
Besides, the foregoing structure of the first and second support sections
212, 214 can be also applied, for example, to vibration gyro sensors each
including the driving means 122 and the reference means 140 as shown in
FIGS. 71 and 72.
The vibration gyro sensor according to a fifty-fourth embodiment shown in
FIG. 71 is constructed such that the first and second support sections
212, 214 are provided in place of the support section 76 of the vibration
gyro sensor according to the fifty-first embodiment shown in FIG. 67. The
vibration gyro sensor according to a fifty-fifth embodiment shown in FIG.
72 is constructed such that the first and second support sections 212, 214
are provided in place of the support section 76 of the vibration gyro
sensor according to the fifty-second embodiment shown in FIG. 68.
The vibration gyro sensor constructed by the integrated fired product made
of ceramics can be formed as the integrated stacked structure comprising
the thin plate layer 22, the substrate layer 24, and the spacer layer 26
as shown in FIG. 2. Alternatively, as shown in FIG. 73, the vibration gyro
sensor can be constructed by using an additional layer (intermediate
layer) 216 which is allowed to intervene between the thin plate layer 22
and the substrate layer 24.
The thickness of the intermediate layer 216 is appropriately 1 .mu.m to 500
.mu.m, preferably 10 .mu.m to 400 .mu.m, and more preferably 50 .mu.m to
300 .mu.m. If the thickness exceeds 500 .mu.m, bending is difficult, and
hence the sensitivity is lowered. By contrast, if the thickness is thinner
than 1 .mu.m, the strength is low, and a problem arises in that the
intermediate layer 216 tends to suffer breakage. Accordingly, it is
preferable to adopt the foregoing range for the thickness of the
intermediate layer 216.
The formation of the intermediate layer 216 is preferred in order to ensure
the strength and improve the sensitivity, concerning the vibration gyro
sensors of the type in which the block-shaped vibrators 2 are supported by
the thin-walled first plate-shaped sections 6 (see FIGS. 1, 4 to 18, and
38 to 41), and concerning the vibration gyro sensors of the type in which
the support base 100 integrally provided with the four block-shaped
vibrators 102A to 102D is supported by the thin-walled plate-shaped
sections 116 (see FIGS. 22 and 24 to 37).
The intervention of the intermediate layer 216 is also advantageous in
order to ensure adequate strength and improve the sensitivity for those of
the type in which the vibrator 2 is constructed by the thin-walled first
plate-shaped section 6, as in the vibration gyro sensors according to the
thirty-first to fifty-fifth embodiments shown in FIGS. 42 to 72. Examples
of such construction are shown in FIGS. 74 to 76.
An embodiment shown in FIG. 74 is illustrative of a structure in which the
intermediate layer 216 is allowed to intervene between the thin plate
layer 22 and the substrate layer 24 for constructing the vibration gyro
sensor according to the thirty-third embodiment shown in FIG. 45. An upper
surface portion 32a of the frame 32, upper portions 6a of the first
plate-shaped sections 6, upper end portions 8a of the second plate-shaped
sections 8, and the third plate-shaped section 10 are formed in an
integrated manner by processing the thin plate layer 22. An upper portion
32b of the frame 32 except for the upper surface portion thereof, lower
portions 6b of the first plate-shaped sections 6, and upper portions 8b of
the second plate-shaped sections 8 except for the upper end portions
thereof are formed in an integrated manner by processing the intermediate
layer 216. A remaining portion 32c of the frame 32 and remaining portions
8c of the second plate-shaped sections 8 are formed in an integrated
manner by processing the substrate layer 24. The layers are stacked and
integrated with each other, followed by firing. Thus the vibration gyro
sensor according to the thirty-third embodiment is produced.
An embodiment shown in FIG. 75 is illustrative of a structure in which the
intermediate layer 216 is allowed to intervene between the thin plate
layer 22 and the substrate layer 24 for constructing the vibration gyro
sensor according to the thirty-fourth embodiment shown in FIG. 46. An
upper surface portion 32a of the frame 32, upper portions 6a of the first
plate-shaped sections 6, upper end portions 8a of the second plate-shaped
sections 8, and the third plate-shaped section 10 are formed in an
integrated manner by processing the thin plate layer 22. An upper portion
32b of the frame 32 except for the upper surface portion thereof, lower
portions 6b of the first plate-shaped sections 6, and upper portions 8b of
the second plate-shaped sections 8 except for the upper end portions
thereof are formed in an integrated manner by processing the intermediate
layer 216. A remaining portion 32c of the frame 32, remaining portions 8c
of the second plate-shaped sections 8, and the block sections 70 are
formed in an integrated manner by processing the substrate layer 24. The
layers are stacked and integrated with each other, followed by firing.
Thus the vibration gyro sensor according to the thirty-fourth embodiment
is produced.
An embodiment shown in FIG. 76 is illustrative of a structure in which the
intermediate layer 216 is allowed to intervene between the thin plate
layer 22 and the substrate layer 24 for constructing the vibration gyro
sensor according to the thirty-fifth embodiment shown in FIG. 47. An upper
surface portion 32a of the frame 32, upper portions 6a of the first
plate-shaped sections 6, upper end portions 8a of the second plate-shaped
sections 8, and the third plate-shaped section 10 are formed in an
integrated manner by processing the thin plate layer 22. An upper portion
32b of the frame 32 except for the upper surface portion thereof, lower
portions 6b of the first plate-shaped sections 6 formed with a plurality
of holes 218 (for constructing the recesses 72 shown in FIG. 48 together
with the thin plate layer 22), and upper portions 8b of the second
plate-shaped sections 8 except for the upper end portions thereof are
formed in an integrated manner by processing the intermediate layer 216. A
remaining portion 32c of the frame 32 and remaining portions 8c of the
second plate-shaped sections 8 are formed in an integrated manner by
processing the substrate layer 24. The layers are stacked and integrated
with each other, followed by firing. Thus the vibration gyro sensor
according to the thirty-fifth embodiment is produced.
As described above, in the vibration gyro sensors according to the first to
fifty-fifth embodiments, the vibrators 2 (or 102), the support base 4 (or
100), the attachment frame 30, 36, 38, the frame 32. (or 104), and other
components are constructed as a whole by the integrated fired product made
of ceramics (non-conductive substances) represented by zirconia oxide.
Accordingly, the present invention is advantageous in that external wiring
can be directly wired and formed thereon by means of the film formation
method. In addition to this advantage, the film formation method such as
screen printing is used to form the electrodes of the
piezoelectric/electrostrictive elements 12, 14, 118, 120, 142.
Accordingly, the present invention is also advantageous in that when the
electrodes of the piezoelectric/electrostrictive elements 12, 14, 118,
120, 142 are formed, the wiring for these electrodes can be simultaneously
extended up to the frame section (frame 104) so that the vibration
characteristics are not affected. Therefore, it is possible to realize
improvement in yield and easy production of the vibration gyro sensor.
In the respective embodiments of the illustrated vibration gyro sensors,
the thin-walled second plate-shaped sections 8 are depicted as those
having the planar plate configuration in any case. However, the present
invention is not limited to those having the planar plate configuration.
It is allowable to use a structure in which the rigidity is lowered in
order to easily vibrate the vibrators in their desired vibration
directions. It is needless to say that no problem occurs at all when those
having a partially constricted shape are used.
As clarified from the foregoing description, the vibration gyro sensor
according to the present invention is constructed as a whole by the
integrated fired product made of ceramics, and no magnetic material is
used at all. Therefore, it is completely unnecessary to consider any
influence exerted on the characteristics by the ambient magnetic field,
and the vibration gyro sensor does not undergo any restriction concerning
its installation place or the like. Further, the large displacement is
obtained by using the first and second plate-shaped sections in the
detecting and driving directions of the vibrators. Moreover, the vibration
gyro sensor has the integrated structure in which the
piezoelectric/electrostrictive element directly contacts with the
vibrator. Accordingly, the large output is effectively obtained, and any
cause to lower the sensitivity due to absorption of stress is effectively
dissolved. Thus the highly sensitive sensor is advantageously provided.
The combined sensor according to the present invention is different from
the conventional sensor which has only one function for one element. The
combined sensor makes it extremely easy to provide another sensor in the
integrated manner adjacent to the vibration gyro sensor. For example, it
is possible to easily realize the structure in which the vibration gyro
sensor and the acceleration sensor are simultaneously provided as one
element (integrated sensor).
Top